Itchy cats might not be as common as itchy dogs, but for some reason they strike fear into the heart of every vet. It’s not uncommon for busy or less confident vets to reach for the steroids, hoping to pass the problem to the next vet when the cat relapses, but feline pruritus doesn’t have to be complicated! In this article, we’re going to go over the diagnosis of feline atopy (now renamed Feline Atopic Skin Syndrome or FASS) and give you actionable tips to help you get a definitive diagnosis.
1. Don’t assume it’s just fleas
Yes, fleas are extremely common in cats. And yes, Flea Allergy Dermatitis (FAD) is the most common cause of feline pruritus. But it isn’t the only cause of itching in cats. While FAD definitely needs ruling out, don’t lose sight of your other differential diagnoses. They are:
- Flea allergy/fleas
- Other external parasites (including Cheyletiella, Notedres, Otodectes, Demodex)
- Ringworm/dermatophytosis
- Food allergy
- FASS
- Malessezia dermatitis
- Pemphigus (note – often itchy in cats)
- Hypersensitivity reaction
- Drug reaction or injection site reaction
- Psychogenic pruritus (especially ventrum)
- Epitheliotrophic lymphoma
- Paraneoplastic syndrome
- Erythema multiforme
2. Know the key clinical patterns
When it comes to narrowing down the causes of pruritus in cats, lesion appearance and distribution is important. Like FAD, FASS tends to cause miliary dermatitis, pruritus of the face, head, and neck, self-induced alopecia, and even eosinophilic plaques, usually on the caudal hind limb. Facial eosinophilic granuloma complex signs (swollen chin, mouth lesions) are also signs of feline atopy. If a cat presents with two or more of the signs above, FASS should be high on your differential list. On the other hand, f ine atopy doesn’t tend to cause erosions/ulcerations on the front legs, axillary lesions, sternal lesions, or tumours – the presence of any of these reduces the chance of FASS being the culprit.
3. Take a detective-level history
As with canine atopy, when it comes to FASS you’ll need to quiz the owner carefully to help rule out some of the differentials. With a thorough history, several of the differentials can be ruled out or made very unlikely in the consult room. Don’t forget to ask about:
- Past flea prevention, including what has been applied, how it has been applied, and how often it has been applied.
- Lesions or pruritus in other pets and people in contact
- Seasonality of the symptoms
- Recently used medications (or shampoos!)
- Other extra-cutaneous symptoms (such as flatulence, vomiting, or diarrhoea (but please note, presence of this does not exclude FASS as a possibility)
4. Don’t assume indoor cats or non-seasonal cases aren’t FASS
Just because your patient is kept indoors, doesn’t exclude FASS. And non-seasonal cases don’t rule out FASS either. In fact, as with dogs, the most common allergen for cats to develop a reaction to is house dust mites. This means they can react year-round. It’s thought about 75% of FASS sufferers have non-seasonal symptoms.
5. Rule out more differentials with easy tests in-house
As when working up an itchy dog, many of the differentials for feline pruritus can be ruled out in the consult room. That said, making it look too easy can devalue your skills – another option is to book the cat in the following day (or admit them to prep) for you to take your samples. Sedation may be needed for many cats.
Here’s what you should take:
- Flea comb (look for fleas and lice)
- Hair brushing (microscopic examination of debris for mites, also useful for ringworm culture)
- Tape strips (look for mites, malassezia and staphylococci in large numbers which suggests a bacterial or yeast dermatitis. While this can be secondary, it can be primary and needs treating either way)
- Skin scrapes (this may be difficult in the non-sedated cat – look for demodex and other mites)
- Ear swab (for mites, may also reveal malessezia/bacterial overgrowth)
6. You’ll need to do a diet trial
As with dogs, a strict novel protein or hydrolysed diet trial is needed for 8-12 weeks in order to diagnose FASS. Partial or complete resolution of symptoms suggests the cat is suffering from a food allergy, or potentially both. Don’t forget, the restricted diet is only half the test – the other half is the ‘challenge’ bit, which is necessary to both confirm that any improvement wasn’t coincidental, and also to identify the offending allergen. Common allergens include lamb, fish, beef, poultry, and egg.
7. Don’t be afraid to refer difficult cases
If the above is filling you with dread, don’t be afraid to refer. As with canine atopy, feline atopic skin syndrome can be complicated to diagnose and frustrating to treat. In many cases, early referral can reduce costs for the pet owner and result in a better outcome for the cat.
8. Keep learning—stay ahead in dermatology
Alternatively, if the above sounds manageable, my final tip is to keep studying dermatology! Dermatology cases require confidence in history-taking, diagnostics, and management, as well as client communication and a clear thought process. The good news is this can be learned. Investing in dermatology CPD can help you improve your patient outcomes and reduce referrals, helping you keep more cases in house. With a postgraduate certificate in small animal dermatology, you can even consider seeing referrals yourself.
Consider Feline Atopic Skin Syndrome in all itchy cats!
Next time you see an itchy cat, don’t just reach for the long-acting steroid. You’ll need patience, and a structured approach, but a diagnosis is possible and opens up significantly more treatment options, improving the patient’s quality of life and reducing the risk of iatrogenic disease. If you want to master dermatology and manage feline skin cases with confidence, our Dermatology Program may be of interest. Or if cats are more your thing, consider our Feline Practice Program instead.
P.S Don’t forget that reading this article counts as CPD – we’d recommend logging it as ‘veterinary reading’. Remember to reflect on your CPD too by making a note about what you’ve learned and whether it will change your approach to pruritic cats in the future.
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Written by: Dr Joanna Woodnutt BVM BVS MRCVS
References:
Clinical signs and diagnosis of feline atopic syndrome: detailed guidelines for a correct diagnosis – Santoro – 2021 – Veterinary Dermatology – Wiley Online Library