What is atopy or atopic dermatitis of cats?

It’s worth starting with the fact that atopy and atopic dermatitis are not exactly the same thing, at least not in humans.

Atopy is the general name of the entire condition and atopic dermatitis is the umbrella term for its manifestations at skin level. Besides skin issues, people also get atopy-related respiratory symptoms (like hay fever or asthma). These happen in cats too, but rarely, so their atopic dermatitis is often the only way in which their atopy reveals itself.

So, what is feline atopy? It is an allergic condition or hypersensitivity that some cats have to allergens in their environment.

This predisposition towards a ‘trigger-happy’ immune system and therefore, atopy and allergies in general, is inherited. For example, atopic cats can have flea allergies or food allergies at the same time.

The age at which cats get diagnosed with atopy varies but they are usually young cats, under 3 years old. There’s no difference between sexes, male and female cats get atopy at the same rate. The breeds with an increased predisposition are the Abyssinian, Devon Rex, Himalayans, Maine Coons and Persians.

What is most likely to trigger atopic symptoms in cats?

The most common atopy-related allergens that come to mind are grasses and pollen, but in fact the list is much longer and is not restricted only to outdoor things, unfortunately. Cats with atopy can be allergic to:

GRASSES

• Meadow grass (Poa pratensis)

• Meadow fescue (Festuca elatior)

• Orchard grass (Dactylis glomerata)

• Perennial rye (Lolium perenne)

• Redtop (Agrostis alba)

• Sweet vernal (Anthoxanthum odoratum)

• Timothy grass (Phleum pratense)

WEEDS

• Dandelion (Taraxacum officinale)

• Dock (Rumex crispus)

• Lamb's quarters (Chenopodium album)

• Mugwort (Artemisia vulgaris)

• Nettle (Urtica dioica)

• Ox-eye daisy (Chrysanthemum leucanthemum)

• Plantain (Plantago lanceolata)

• Ragweed (Ambrosia artemisiifolia)

• Red clover (Trifolium pratense)

TREES & SHRUBS

• Alder (Alnus serrulata)

• Ash (Fraxinus americana)

• Beech (Fagus grandifolia)

• Birch (Betula populifolia)

• Hazelnut (Corylus americana)

• Oak (Quercus rubra)

• Privet (Ligustrum vulgare)

• Willow (Salix nigra)

The plant allergens can be either the plant’s pollen or the proteins in its cells which are released when the plant cells are crushed (as when the grass is cut, for example).

STORAGE MITES

• Acarus siro

• Lepidoglyphus destructor

HOUSE DUST MITES

• Dermatophagoides farinae

• Dermatophagoides pteronyssinus

DANDER

• human epithelia (yes, sadly, your cat can become allergic to you!)

MOULDS

• Alternaria type (Alternaria tenuis)

• Aspergillus mix (A. amstelodami, A. flavus, A. fumigatus, A. nidulans, A. niger)

• Penicillium mix (P. camembertii, P. chrysogenum, P. digitatum, P. chrysogenum, P. roquefortii)

The allergens can be either the plant’s pollen or the proteins in its cells which are released when the plant parts are crushed (as when the grass is cut, for example). Initially the allergens are breathed in and meet the respiratory immune system but later, as the allergy unravels the skin barrier, microbes and irritants can also come in contact with the immune system of the skin and make the symptoms even worse.

What symptoms do cats with atopic dermatitis have?

Cats with atopy usually show an initial severe itchiness, followed by:

• skin rashes,

• hairless areas,

• lip sores,

• frequent ear infections.

The areas where this is most obvious are the head, ears, neck, chest and flanks, lower belly and back of the thighs.

When to call your vet

If you suspect that your cat may have atopy, it’s recommended to speak to a vet as soon as possible.

Allergies of any kind do not go away by themselves. With atopy, the produced antibodies can vary in concentrations depending on the time of the year, giving milder or worse symptoms (allergic flare-ups).

But overall these flare-ups only tend to get worse and happen at shorter and shorter intervals if measures are not taken to reduce or eliminate the immune reaction they cause.

How is cat atopy diagnosed?

As described in the overview article on hypersensitivities, identifying allergies is done by excluding (or confirming) them one by one.

In order to correctly diagnose a cat with atopy, the vet will first exclude:

• non-allergic skin issues,

• flea allergic dermatitis with a test or an effective flea control,

• food allergies with a food trial.

Both flea and food allergies are more common in cats than atopy.

A thorough medical history will be taken and a complete exam of your cat done to determine if atopy is their (main) allergy type. This will be more likely if your cat:

• is younger than 3 years old,

• is of a predisposed breed,

• shows symptoms that vary in intensity with the time of the year,

• started itching first, then got rashes and other visible skin changes.

How is cat atopy treated?

For cats with mild symptoms antipruritic medication can sometimes be sufficient for managing the seasonal worsening of their atopic dermatitis.

For cats with bad symptoms, the treatment has a short-term and a long-term part.

In the short term the vet will also use medication to stop the itching and also anti-inflammatories and antibiotics to treat secondary infections and allow the skin to calm down and heal.

Long-term, the plan for these cats usually starts with identifying what exactly they are allergic to, either by serological or intradermal skin testing.

For serological testing, a blood sample is taken from the cat and sent to the lab where they measure the concentrations of antibodies against the allergens listed at the beginning of the article. This is usually done at most vet practices.

The intradermal skin testing is similar to the one done in humans, on a patch of (shaved) skin a small quantity of different allergens is injected and the skin reaction to each is measured after a short period of time. Cats obviously don’t sit willingly for this, so they need to be sedated for the test. Since the allergen solutions are not that easy to get, only dermatology specialists do this type of testing.

For the test results to be reliable, the cats have to be at least 12 months old and not have had immunity-influencing medication within a certain period of time.

Allergen identification through testing is a very important step - it helps you avoid allergens where possible and the vet determine which allergens should be included in the immunotherapy treatment.

Antigen-specific immunotherapy (ASIT) or simply ‘immunotherapy’ is one way of preventing future atopic flare-ups. Another option is using medications that either suppress the immunity temporarily or contain antibodies against the allergen-specific antibodies.

The best treatment plan will depend on individual factors, but immunotherapy is widely recommended by vets because it has almost no side effects.

What can you do to help your atopic cat?

It may make you feel very helpless to see your cat itching badly out of the blue, but there are many things you can do:

• Keep a strict parasite control for all pets in your household. Even without a flea allergy on top of their atopy, flea bites or mites can further irritate an atopic cat’s skin.

• Remember the indoor allergens (dust and storage mites) - remove rugs where possible, vacuum and mop as often as possible, use HEPA filters, wash bedding and toys at 60°C if possible, seal in vacuum bags and freeze for 72 hours what’s not washable.

• If your cat doesn’t have food allergies as well, use skin supporting foods and supplements.

Atopy can be incredibly frustrating for you to deal with. Don’t struggle with it on your own, FirstVet is here 24/7 so you can book an appointment with us at any time to speak to one of your vets about it!