Many cat owners would rather suffer than give up their moggy, but there are other options.
Cat allergies left untreated can lead to chronic illness, but for many sufferers, avoidance is not an option .
Now German researchers have reviewed the evidence on cat allergy and treatment, taking into account the very important element of love.
According to their findings, the incidence of cat allergy in children and young adults has risen, particularly during the pandemic, with numbers ranging from 19% to 26% in various age groups and northern European study cohorts.
But unlike many allergy treatment situations, avoidance is often off the table.
Even gathering data from individual patients can be complicated, with patients frequently claiming that they only experienced a reaction to cats other than their own, despite displayed allergic phenotypes, like a nasal tone, suggesting otherwise.
But, reassuringly, there is data to show that allergic cat owners won’t necessarily spend the rest of their lives scratching and sneezing.
“Some cat owners, despite manifest allergy, seem to have actually reached a stage of tolerance during living with the cat. IgG4 immunoglobulins have been discussed for years as a mechanism of tolerance in cat allergy. These are formed during chronic and high antigen exposure and could thus transform an initially unfavourable Th2 immune response into a protective Th2 response,” the authors said.
The allergen, Fel d 1 is the most significant biomarker for sensitisation and clinically relevant cat asthma and cat allergy, and can be found in the air, in beds and in litter boxes. Studies showed a dose-response relationship between the amount of allergen present and the risk of sensitisation, especially in children aged one or under.
But after the age of one, the risk of sensitisation in families without cats increased by 6% more than in households with cats until the risks reached parity around the age of 16.
If a child has a parent with a cat allergy, there is a 30-60% chance that it will be passed on to them, the authors said.
Some guidelines suggest that if there is a predisposition to allergies, and the household wants a cat, they should wait until after the first few months of the child’s life, but there is research suggesting early exposure is protective.
Danish studies have shown high levels of exposure to cats in early childhood prevent asthma until the age of 12 and a mild protective effect against eczema and allergic rhinitis. In Japan, researchers found an association between early childhood exposure to cats and lower rates of allergy to egg, wheat and soy.
“Counselling pet owners requires special empathy in allergy consultations, because allergen avoidance is not enforceable in the vast majority of cases,” the authors warned.
Keeping that in mind, they suggest the following management strategies:
- Explain the consequences of continued exposure, especially for those with atopic risk, and that exposure can occur without owning a cat, through contact with those who do.
- Emphasise the need to keep cats out of bedrooms.
- Advise on textile hygiene – washing detergents, machine cycles and tumbler dryers.
- Suggest air filtration devices with HEPA filters in all rooms to prevent cat asthma, which have been proven to provide immediate relief as well as prevent late phase reactions.
- Indoor cats create a much higher allergen load, outdoor cats less.
- Hairless cats still secrete Fel d 1 through their saliva, but there may be less of it distributed around the house.
- Recommended drug therapies are still antihistamines, or mast cell stabilisers, including cromoglicic acid (nasal spray, eye drops) and asthma spray (such as formoterol, plus corticosteroid), to be taken before visiting an environment with a cat.
- Topical H1 receptor blockers can be useful for contact urticaria.
- Along with genetic predisposition, environment may also be a factor in atopy. “This can be countered by so-called ‘green spaces’, which contribute to a richness of the (intestinal) microbiota,” the authors suggested.
- Address zinc and folate and iron deficiencies. “Anaemia has been significantly linked to the risk of developing atopy and subsequent allergic symptoms in international studies,” the researchers said. The problem is specifically iron utilisation disorder, which is not an absolute deficiency and is harder to detect, they said. “In situations when the so-called ‘labile iron pool’ in macrophages and other regulatory cells is reduced, they cannot fulfil their immunomodulatory role and become pro-inflammatory. In a setting of iron deficiency, the pro-allergic Th2 cells also survive longer than Th1 cells and drive the immune response further towards allergy.”
Meanwhile, there isn’t conclusive evidence for allergen immunotherapy, with subcutaneous therapy showing a high rate of systemic reactions, albeit improvement in symptoms, quality of life, asthma control and medication use.
A Swiss vaccine for cats that immunises them against Fel d 1, removing the source of the allergy altogether, has been developed but it is unlikely to be available for a couple of years. Additionally, cat food containing chicken IgY anti-Fel d 1, which cuts down on the cat’s allergen excretion, is already commercially available, though results vary.
Also in the pipeline are biologics, specifically a combination of monoclonal IgG4 anti-Fel d 1 IgG4 antibodies applied subcutaneously, which shows promise for preventing allergic rhinitis and asthma symptoms.