What are allergies, and how do they affect dogs?

One of the most common conditions affecting dogs is allergy. In the allergic state, the dog’s immune system “overreacts” to foreign substances (allergens or antigens) to which it is exposed. These overreactions are manifested in three ways. The most common is itching of the skin, either localised (one area) or generalised (all over the dog). Another manifestation involves the respiratory system and may result in coughing, sneezing, and/or wheezing. Sometimes, there may be an associated nasal or ocular (eye) discharge. The third manifestation involves the digestive system, resulting in vomiting or diarrhoea. The specific response that occurs is related to the allergen and the individual animal’s immune system.

What is meant by the term flea allergy?

In spite of common belief, a normal dog experiences only minor skin irritation in response to flea bites. Even in the presence of dozens of fleas, there will be very little itching. On the other hand, the flea allergic dog has a severe, itch-producing reaction to flea bites. This occurs because the dog develops an allergic response to the flea’s saliva. When the dog is bitten, flea saliva is deposited in the skin. Just one bite causes intense itching and this is of a long lasting nature.

What does this reaction do to the dog?

The dog’s response to the intense itching is to chew, lick, or scratch. This causes hair loss and can lead to open sores or scabs on the skin, allowing a secondary bacterial infection to begin. The area most commonly involved is over the rump (just in front of the tail). This is probably because fleas find this part of the dog more desirable. Many flea-allergic dogs also chew or lick the hair off their legs.

What is the proper treatment?

The most important treatment for flea allergy is to get the dog away from all fleas. Therefore, strict flea control is mandatory and this involves ensuring the dog is flea-free and also removing fleas from the environment. There are many products available for flea control, and many work in entirely different manners. In some cases, multiple products may be needed. Some are used on the dog and some on the dog’s environment. Unfortunately, complete flea control is invariably difficult, particularly with dogs living outdoors in summertime when the weather is warm and humid, where a new population of fleas can hatch out every 7 days. Some dogs can be desensitised to the adverse effects of flea bites. Flea saliva extract (flea antigen) is injected into the dog in tiny amounts over a prolonged period of time. This is an attempt to reprogram the dog’s immune system so it no longer over-reacts to flea bites. If successful, itching no longer occurs or is less intense when the dog is bitten. However, this approach is only successful in less than 30% of cases.

When strict flea control is not possible, mediations can be used to block the allergic reaction and give relief. This is often a necessary part of dealing with a flea allergy. Some medications can have side affects and for this reason a Veterinary consultation is often required. Some dogs develop a secondary bacterial infection in the skin. When this occurs, appropriate antibiotics must be used and steroid therapy reduced even further.


Where does my cat get fleas from?

The most common flea found on cats and dogs is the cat flea (Ctenocephalides felis). Rarely rabbit fleas or stick-fast fleas are found on cats.

The most important source of cat fleas is newly developed adult fleas in pupae in your house. Adult fleas live and feed on animals but the female lays eggs which fall off into the environment. Under favourable conditions these eggs develop first into larvae and then into pupae. The pupae contain adult fleas which lie in wait for a suitable animal host. Modern carpeted centrally heated homes provide ideal conditions for the year round development of fleas. The highest numbers of flea eggs, larvae and pupae will be found in areas in the house where pets spend most time such as their beds, the furniture and so forth. Even though fleas may be in your house you probably won’t see them; the eggs are too small to see without magnification and the larvae which are just visible migrate deep down into carpets, furniture or cracks in floors away from the light. The flea life cycle is most active in the warm, humid months, so fleas are worst in late Spring, Summer and Autumn.

What effect do fleas have on my cat?

Many cats live with fleas but show minimal signs. The following problems can occur:-

  • • Some cats develop an allergy to flea bites. If these cats are exposed to fleas they groom or scratch excessively and develop skin disease, typically so-called ‘miliary’ dermatitis.
  • • Adult fleas live on animals and feed on blood. In kittens and debilitated animals this may cause anaemia. With heavy infestation this flea-anaemia can be life-threatening.
  • • The flea acts as the intermediate host for the tapeworm ( Dipylidium caninum). Tapeworm eggs which are shed within tapeworm segments in cat faeces are eaten by flea larvae which develop into infected fleas. Cats become infested by eating infected fleas during grooming. Any cat with fleas is likely also to have a tapeworm infestation.

How can I get rid of fleas on my cat?

This can be a demanding task and requires a three pronged approach. Fleas need to be eliminated from your cat, from any other cats and dogs that you own and from your home. Even this rigorous approach may not give 100% control as there are other sources of fleas that are not amenable to your control such as other people’s pets, wild animals and infested environments which your cat may come into contact with outside your house.

What products are available to treat my cat?

Insecticides applied to cats are designed to kill adult fleas. Many products have limited effectiveness because they only work for a few hours after application. This is particularly a problem with flea shampoos and powders; they kill fleas present on your cat at the time of application but have little residual effect so the day after use the cat may again have fleas.

There are now some newer products available from your vets which have good residual action. The ‘new generation’ flea control products have revolutionised the control of fleas – if applied as directed, fleas are unlikely to be a problem.

ALWAYS READ THE LABEL CAREFULLY – apply the product as instructed and repeat at the intervals stated.

My cat hates being sprayed. What can I do?

Many cats strongly dislike being sprayed. Consult your vet, there are several alternatives available. Flea collars are very convenient but they don’t work well enough to cope in the face of an infested environment or provide sufficient control for a flea allergic cat. Some cats will develop a skin reaction to collars. There are several insecticides which are formulated as “spot ons”; these contain a small volume of liquid which is applied onto the cat’s skin on the back of its neck

How can I treat my home environment?

A number of different products are available which will kill the stages of the flea life cycle present in your home such as:-

  • • insecticide sprays for use on the house
  • • sprays containing insect growth regulators for use on the house
  • • mediations which stop the growth development of the fleas are available. Adult fleas which feed on the medicated animal produce eggs which are incapable of hatching to produce adult fleas so the development of an infested environment is prevented.
  • • insecticides applied by professional pest control operatives to your house

Sprays for use on the house should obviously be used in places where the flea eggs, larvae and pupae are likely to be. It is worth initially going over the whole of the house and then concentrating on the hot spots – your cat’s favourite dozing spots – such as soft furniture, beds and carpets. Once they hatch from the egg flea larvae move away from the light deep into carpets and into other nooks and crannies and it can be difficult to get insecticides into these places. So be sure to move cushions and to move furniture and beds to spray underneath. Other places liked by larvae are skirting boards and the cracks in wooden floors.

Your pet’s bedding should be regularly washed at a high temperature or replaced. Regular and thorough vacuuming of your carpets, floors and soft furnishings can remove a large proportion of the flea eggs, larvae and pupae which are present in your home. You will need to throw away and preferably burn the dust bag to prevent eggs and larvae developing in there. Vacuuming prior to the application of a spray to the house is recommended because the vibrations will encourage newly developed fleas to emerge from pupae which will then be killed by the insecticide.

ALWAYS READ PRODUCT LABELS CAREFULLY – apply as instructed, use the quantity suggested and repeat at the intervals stated.

How do I choose which products to use?

A flea control programme needs to be individually tailored and take into account your reasons for doing flea control and the lifestyle of your cat and other pets. Your vet with his knowledge of the advantages and limitations of the products available is the best person to advise you about this.

Are insecticides safe for my cat and my family?

Insecticides for flea control should be safe both for animals and humans provided the manufacturer’s instructions are carefully followed. One should be particularly careful to avoid combining insecticides with similar modes of action. Always seek your vet’s advice if you are unsure about this and always tell your vet about any flea control products you may be using other than those which he has prescribed.

Certain types of pets (e.g. fish, amphibia, reptiles, birds and invertebrates) may be particularly susceptible to some products. Do not use any flea control products in the room in which these pets are kept without first consulting your vet for advice.

I have not seen any fleas on my cat. Why has my vet advised flea control?

Fleas are easy to find if a cat is heavily infested. If fleas are present in smaller numbers it can be harder to see them and they move fast. Try looking on the cat’s belly, around the tail base and around the neck. Sometimes adult fleas cannot be found but “flea dirt” can be seen. This is faecal matter from the flea which contains partially digested blood and is a good indicator of the presence of fleas. Flea dirts are small black specks or coiled structures; if you are not sure place them on damp white tissue and they will dissolve leaving a reddish brown blood residue. Flea dirts may be found in cat’s bedding even when they cannot be found on the cat.

In cats that develop an allergy to fleas one of the symptoms is excessive grooming. Cats are very efficient at removing debris from their coat’s using their tongues and may succeed in removing all evidence of flea infestation i.e. adult fleas and flea dirt. One of the commonest causes of feline allergic skin disease is flea allergy. To investigate this possibility your vet may advise rigorous flea control even though no fleas can be found. If the cat’s skin problem improves with flea control then it suggests that flea allergy is involved.

I noticed my cat had fleas after his return from the boarding cattery. Did he get them at the cattery?

Not necessarily. Newly hatched adult fleas can survive for up to 140 days within the pupa. When you and your pets are absent from home for extend periods of time these adult fleas will remain in the pupae because no host is available. As soon as you or your pet returns these fleas will suddenly emerge in large numbers and jump onto cats, dogs and even people in the search for a blood meal.

Despite treating my cat for fleas he still has them. Is there a superflea?

There is no evidence of fleas developing significant resistance to insecticides. Apparent failure of treatment almost always results from inadequate treatment of the home or exposure to other infested environments. Consider treating garden sheds, cars and in the summer favoured outdoor sleeping spots. Bear in mind that your cat may be going into other people’s houses. A lot of these problems can be overcome by using a really effective and persistent product on the cat to kill adult fleas (particularly the ‘new generation’ of fleaicides) in addition to treating your home.


What should I do to kill the fleas on my dog?

This is a simple question with a rather complex answer. Successful flea control has two aspects. Fleas must be controlled on your dog, and fleas must be controlled in your dog’s environment. Since dogs and cats share the same fleas, the presence of a cat in your dog’s environment makes flea control much more difficult.

To appreciate the complex issue of flea control, you must understand something about the life cycle of the flea.

Fleas seem to be rather simple creatures. How complicated can their life cycle be?

Although you are only able to see the adult flea, there are actually 4 stages of the life cycle. The adult flea constitutes only about 5% of the entire flea population if you consider all four stages of the life cycle. Flea eggs are pearly white and about 1/2 mm (1/32 in). in length. They are too small to see without magnification. Fleas lay their eggs on the dog, but the eggs do not stick to the dog’s hair. Instead, they fall off into the dog’s environment. The eggs make up 50% of the flea population. They hatch into larvae in 1 to 10 days, depending on temperature and humidity. High humidity and temperature favour rapid hatching.

Flea larvae are slender and about 2-5 mm (1/8 – 1/4) in length. They feed on organic debris found in their environment and on adult flea faeces, which is essential for successful development. They avoid direct sunlight and actively move deep into carpet fibres or under organic debris (grass, branches, leaves, or soil). They live for 5 to 11 days and then pupate.

Moisture is essential for the survival of these immature stages of the flea; larvae are killed by drying. Therefore, it is unlikely that they survive outdoors in shade-free areas. Outdoor larval development occurs only where the ground is shaded and moist and where flea-infested pets spend a significant amount of time. This allows flea faeces to be deposited in the environment. In an indoor environment, larvae survive best in the protected environment of carpet or in cracks between hardwood floors. They thrive in warm conditions such as the recent summer.

Following complete development, the mature larvae produce a silk-like cocoon in which the next step of development, the pupa, resides. The cocoon is sticky, so it quickly becomes coated with debris from the environment. This serves to camouflage it. In warm, humid conditions, pupae become adult fleas in 5-10 days. However, the adults do not emerge from the cocoon unless stimulated by physical pressure, carbon dioxide, or heat.

Pre-emerged adult fleas can survive up to 140 days within the cocoon. During this time, they are resistant to insecticides applied to their environment. Because of this, adult fleas may continue to emerge into the environment for up to 3 months following insecticide application.

When the adult flea emerges from its cocoon, it immediately seeks a host because it must have a blood meal within a few days to survive. It is attracted to people and pets by body heat, movement, and exhaled carbon dioxide. It seeks light, which means that it migrates to the surface of the carpet so that it can encounter a passing host. Following the first blood meal, female fleas begin egg production within 36 to 48 hours. Egg production can continue for as long as 100 days, which means that a single flea can produce thousands of eggs.

This entire life cycle (adult flea –> egg –> larva–> pupa –> adult) can be completed in 7 – 21 days with the proper temperature and humidity conditions. This adds to the problem of flea control.

What can these fleas do to my dog?

If untreated, the female flea will continue to take blood for several weeks. During that time, she will consume about 15 times her body weight in blood. Although the male fleas do not take as much blood, they, too, contribute to significant blood loss from the host animal. This can lead to the dog having an insufficient number of red blood cells, which is known as anaemia. In young or debilitated dogs, the anaemia may be severe enough to cause problems.

Contrary to popular belief, most dogs do not itch too much due to fleas. However, many dogs become allergic to the saliva in the flea’s mouth. When these dogs are bitten, intense itching occurs, causing the dog to scratch and chew continuously.

What can I do to rid my dog of fleas?

Successful flea control must rid the dog of fleas and it must rid the dog’s environment of fleas. In fact, environmental control is probably more important than what is done to the dog. If your dog remains indoors and you do not have other pets that come in from the outside, environmental control is relatively easy. However, the dog that goes outdoors or stays outdoors presents a significant challenge. It may be impossible to completely rid the environment of fleas under these conditions, though flea control should still be attempted. When the dog is free-roaming or other dogs are allowed access to the dog’s garden, the task of flea control becomes even more difficult.

What can I do for my dog?

Many insecticides that are applied to the dog have limited effectiveness against fleas because they are only effective for a few hours after application. Also, most of these products are effective only against adult fleas. Flea powders, sprays, and shampoos will kill the fleas present on your dog at the time of application. However, most of these products have little or no residual effects, so the fleas that return to your dog from the environment are not affected. Thus, your dog may be covered with fleas within a day after having a flea bath or being sprayed or powdered.

There are some newer, more effective sprays that can be a valuable part of the overall treatment plan. They kill adult fleas rapidly and are safe enough to use daily, if necessary. Flea sprays containing insect growth regulators are helpful in managing the overall problem because they help to break the flea life cycle. Some of the newer pet sprays with growth regulators are not recommended for daily use; once weekly application is sufficient. Always read the label when using any new flea product on a dog. Recently many more sophisticated products have become available that not only have a high knock-down effect i.e. killing adult fleas on the animal, but also have long residual effects. Some require repeat applications only every several weeks. Tablets, spot on and pour on preparations are all available today. Please discuss the problem with us and we will advise. For example some dogs with sensitive skins are irritated by flea collars and these should not be worn.

What can I do to minimise fleas in the environment?

Environmental flea control usually must be directed at the dog’s immediate environment, the house and any outbuildings occupied by the dog, etc. Even though fleas may be in your house, they are usually never seen Fleas greatly prefer dogs and cats to people; they only infest humans when there has not been a dog or cat in the house for several days. (There are exceptions to this.) You may have the house professionally fumigated or use one of the sprays available today that do have a long residual effect. However before purchasing any of these from a supermarket or pet shop it is worthwhile consulting your veterinary surgeon. He will be able to give you advice regarding many of the newer, safer sprays that available. In situations where there is a very high flea density it may be necessary to repeat environmental control rather more frequently than suggested in the product literature. Again follow the advice of your veterinary surgeon. Some products not only kill the adult fleas but also contain growth regulators that prevent flea maturation. Your veterinary surgeon is able to help you choose the most effective product for your situation. Remember these products will not kill fleas that have not emerged from their cocoon.

I have not seen fleas on my dog. Does that mean that none are present?

When a dog is heavily infested with fleas, it is easy to find them. If the numbers are small, it is best to quickly turn your dog over and look on its belly. If you do not find them there, look on the back just in front of the tail. Be sure to part the hair and look at the level of the skin. When the numbers are very small, look for “flea dirt” Flea dirt is faecal matter from the flea that contains digested blood. Finding flea dirt is a sure indication that fleas are present or have been present recently.

Flea dirt looks like pepper. It varies from tiny black dots to tubular structures about 1/2 mm (1/32 in) long. If you are in doubt of its identification, put the suspected material on a light coloured table top or counter top. Add one or two drops of water, and wait about 30 seconds. If it is flea dirt, the water will turn reddish brown as the blood residue goes into solution. Another method is to put some of the material on a white paper towel and then wet the paper towel with water. A red stain will become apparent if you gently wipe the material across the surface of the paper towel.

Many people find tiny drops of blood in a dog’s bedding or where the dog sleeps. This is usually flea dirt that was moistened, then dried. It leaves a reddish stain on the bedding material and is another sign that fleas are present.

I just got my dog home from boarding and it has fleas. Doesn’t that mean that they were picked up while boarding ?

Not necessarily. If you recall, pre-emerged adult fleas can survive up to 140 days within the cocoon. This is significant when your pets are gone from home for extended periods of time. During the time that the house is quiet and empty, pre-emerged adults remain in their cocoon. Even if the house was treated with an insecticide, their cocoon protects them. When people and pets return to the house, adults emerge from their cocoons and immediately begin to seek a blood meal. They jump on dogs, cats, and even people. Although it may appear that a dog just returned from boarding brought fleas to your home, it is also very possible that a sudden emergence of adult fleas may account for the fleas present. Thus do not be too quick to blame the kennels, after all they do not want fleas any more than you do and any reputable boarding kennels will be engaging in rigorous flea control anyway..

Get in touch with us

Four great Veterinary locations in Sydney Australia
  • Alexandria
  • Dee Why
  • Kingsford
  • Marrickville

Shop 1/138 Botany Rd
Alexandria NSW 2017
Phone: (02) 9698 4120
Fax: (02) 9698 4125
Email: Alexandria@amsvet.com.au

815 Pittwater Rd
Dee Why NSW 2099
Phone: (02) 9972 2044
Fax: (02) 9982 2307
Email: Deewhy@amsvet.com.au

70 Gardeners Rd
Kingsford NSW 2032
Phone: (02) 9662 6703
Fax: Fax: (02) 9662 8829
Email: Kingsford@amsvet.com.au

402 Illawarra Road
Marrickville NSW 2204
Phone: (02) 9558 2500
Fax: (02) 9559 3410
Email: Marrickville@amsvet.com.au

  • Alexandria
  • Dee Why
  • Kingsford
  • Marrickville


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