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  • Dr. Danielle van der Ryst BVSc

Allergies: how to know if your pet has an allergic skin condition?

Updated: Feb 1, 2022

Allergies can be hard to control and are chronic in nature.

Dogs and cats present differently when it comes to allergies. Symptoms most commonly seen in dogs are as follows:

· Itching/scratching

· Chewing or biting paws or other body parts

· Hair loss (alopecia)

· Reddening of the skin (erythema)

· Discoloured fur (more common in white dogs due to excessive licking)

· Chronic ear infections

· Secondary skin infections presenting as small pimple-like lesions

Symptoms most commonly seen in cats:

· Self-inflicted trauma

· Bumps on various areas on the body

· Ulcers on lips

· Patches of missing hair (falling out/being pulled out by the cat)/over grooming

It can be difficult to differentiate between normal grooming behaviour and true itching. Vomiting or defecating hair may be an indicator of excessive itching.

What types of allergies exist and how do we treat them?

There are 3 main types of allergies in relation to skin conditions. It is possible for a pet to have a combination of all three allergy types.

1. Flea Allergy Dermatitis (FAD)

This is a very common cause of skin allergies, even if you do not see a flea on your pet. Correct and effective flea control depends on various factors such as:

  • Environmental challenges (If the environment is of such a nature that the ‘’load’’ of fleas exceed a certain threshold, the environment will also need to be treated with the appropriate products (all products listed below)

  • Season (summer and spring have a significantly higher risk for ticks and fleas. Although these two seasons are a higher risk, winter and autumn can still pose a risk, depending on ambient temperatures and environment)

  • Ensure that you stick to your anti-parasite prevention schedule. Either using a long-acting treatment such as Bravecto (which is active for 3 months) or make sure you give the monthly treatments with products like Nexguard, Frontline and/or Revolution.

Topical control:

Ultrum room/bedding spray

Frontline topical spot-on

Revolution spot-on

Bravecto spot-on

Systemic control (tablet consumed by your pet):



Nexguard spectra

2. Food Allergy

This is the rarest of the 3 allergies that exist. True food allergies are as a result of the food’s protein source. The special (prescription) diets thus reconstitute the protein by breaking it down (commonly referred to as hydrolysing the protein), eliminating the adverse reaction to the protein. Most food allergies in cats will present with gastro-intestinal symptoms, such as vomiting/diarrhoea, but it may also present as blood in the faeces.

To successfully treat allergies we will need to perform a food trial. This consists of a strict dietary change to an anallergenic food. Your pet will need to stay on this dietary trial for at least 8-12 weeks, before any significant improvement can be expected. The most important rule when doing a food trial is NO TREATS OR OTHER FOODS are to be given within this period.

Anallergenic food options include:

  • Hills Prescription Diet z/d (cats and dogs)

  • Royal Canin Anallergenic

  • Hills Prescription Derm Complete

Hypoallergenic food options include:

  • Hills Prescription Derm Defense

  • UltraDog Hypoallergenic

  • Eukanuba Sensitive skin

3. Atopy or Allergic-inhaled Dermatitis

Common allergens that cause this reaction inside your home include dust, dust mites, mould, animal dander and feathers. Outside it may be grasses, trees and shrubs. The allergens can be inhaled, pass through the paw pads and even possibly ingested. Since these compounds are in abundance everywhere, preventing exposure is difficult, if not impossible.

Treatment of this condition varies per individual and life-long, thus can be complicated. It may take a few consults with different protocols before the correct and most effective treatment regime can be found for your pet.

Treatment options include:

Topical treatments (only effective in combination with systemic treatment or if the condition is very mild and localised).


  • Topical spray applied to the skin

  • Effect is relatively rapid with obvious improvement seen after 1-2 weeks.

  • Side effects – none in the short term, but thinning of the skin can be seen with long term use.

Systemic treatment

Apoquel (only in dogs):

  • Tablets given twice daily (loading dose) for 2 weeks then once daily long term

  • Effect is rapid with improvement noted within 4 hours

  • Side effects are minimal and very rare


  • Tablets or liquid can be administered orally

  • Effect rapid

  • Side effects are severe – short term being increased drinking and urination; increased appetite and severe weight gain. Long term effects include muscle wastage, urinary tract infection and serious hormonal related diseases.


  • Capsule administered orally

  • Effects seen only in 4-6 weeks

  • Side effects short term can lead to vomiting or diarrhoea; long term secondary skin infections.

Diagnostic Tests

The necessary diagnostics will depend on history received from owner, signalment (age, breed, gender, etc.) and the physical examination, all of which are discussed below.

Diagnostic tests that your vet may want to run include:

  • Skin scraping – looks for parasites/eggs on your pets’ hair/skin (done in order to eliminate mange as the cause).

  • Fungal test - (A wood’s lamp is used to determine whether ringworm is present).

  • Skin biopsy (to check for auto-immune problems, chronic and deep infections or any cancerous lesions causing skin problems).

  • Food trial – (sometimes as treatment and sometimes as a test to determine whether or not a true food allergy is present).

It is considerably common that if your pet struggles with skin-related issues, they tend to struggle with their ears as well.

It is a not-so-well known fact that ears are an extension of the skin and thus a lot of what is true in skin can be applied to ears too.

Ear infections, most commonly otitis externa, occur in both dogs and cats. This is a condition where the external ear canal becomes inflamed (one or both ears).

Symptoms include:

- Head shaking

- Pawing/scratching at the ears

- Foul odour

- Redness of skin

- Swelling

- Increased discharge/’’wetness’’

- Scaly skin

- Othaematoma in dogs and cats (when the ear swells up with blood due to the excessive scratching)

Otitis externa can be caused by many different factors: some of these factors (parasites/allergies/foreign objects) can cause inflammation directly, while others (bacteria, yeast, middle ear infections) just make it that much worse. The shape and form of your pet’s outer ear (pinna) can be a predisposing factor too.


During the consultation your vet will first perform an ear examination (where check inside their ears with an otoscope). This is done to check for foreign objects, impacted debris, parasite infection and structural integrity of the ear drum. The vet will then perform an ear smear (to be examined under a microscope), which is done to check for abnormal yeast/bacterial populations present in the ear. If the infection has been ongoing for a long time, ear cultures and biopsies may be recommended.


There are topical and systemic treatment options available depending on the individual case, although it is preferable to treat topically as these are usually more effective.

Most topical ear medication contains a combination of antibiotics, antifungals and glucocorticoids (cortisone). It is best not to attempt any home remedies as it may further irritate the ear canal. If inflammation is not severe and there is no overgrowth, a simple ear cleaner will be recommended in place of a highly medicated ear solution.

Othaematoma, unlike the rest of the symptoms mentioned, would need surgical correction, as well as treatment of the underlying infectious agent.

Visit us in the month of February 2022 and receive R200 off on any skin and ear consultation.

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