Pet allergies 4

 

If the child is sneezing because of animal friends: cats, dogs and … ferrets

Allergies to rodent hair are on the rise: what to do if your child is affected?

 

It is not seasonal and can torment you all year round: it is the allergy to animal hair – cats in pole position – that affects at least 10% of children. A new entry in recent years is the allergy to rodents, or rather to the so-called new pets: hamsters, guinea pigs and dwarf rabbits, in addition to cases of allergy to ferret hair. A growing trend at a national level.

 

Alexander Ferns, head of Allergology at the Hanna Pediatric Hospital, says that «The cause of this type of allergic reaction is not actually the hair but a protein, albumin, which is found in the saliva, sebaceous glands and sweat of the pet. This allergen is then spread on the fur when dogs and cats lick themselves to wash themselves». Since it is a very small and volatile molecule (90 out of 100 antigens fly), it is much more harmful than its concentration indicates: from the animal’s coat it spreads easily into the air, sticking to people’s bodies and clothes and remaining in domestic environments even for a long time with great difficulty in elimination.

 

Then there is the new entry `rodents´: «Since they have become pets, increasingly common in homes – continues Ferns- there has been an increase in allergic reactions among children and teenagers. This growing trend is observed at a national level and also among the young patients of Hanna Hospital: about 3 out of 100 show this type of allergy. Not only that: as the latest reports from France indicate, even `fashionable´ animals such as ferrets can cause annoying reactions, first and foremost contact urticaria».

 

The albumin contained in the saliva of domestic animals has a similar structure to bovine albumin, therefore children allergic to cats and dogs are often allergic to milk as well. Conversely (and this is observed especially in teenagers) children allergic to milk and beef have a very high risk of developing an allergy to felines. Whether they are caused by cats and dogs (in particular, about 8% of children are allergic to Fido), or whether the “culprits” are “household” rodents, the allergic reactions are the same. They can manifest themselves in the form of rhinitis, conjunctivitis, urticaria, contact dermatitis. But the main symptom is asthma: the allergenic particles attack the small bronchi which close; the oxygen in circulation is reduced and a condition of hypoxia is generated. The asthmatic reaction caused by this particular allergen is often difficult to recognize because it does not cause a cough or the traditional perception of shortness of breath.

 

Given that the most effective treatment would be to avoid contact with the animal that is the source of the problem, the therapies for the treatment of symptoms are common to those adopted for other types of allergies: in the case of acute rhinitis, antihistamines and cortisone spray are used; for asthmatic manifestations, cycles of corticosteroids can be used; for conjunctivitis, antihistamine eye drops or cortisone ointments are used.

 

For prevention, vaccines are used that can be administered either subcutaneously or under the tongue. The specific desensitization process is quite long – it lasts about 3 years – but it is particularly effective against allergen attacks. Finally, a curiosity: even dogs can develop contact dermatitis. The strange thing is that in some cases it has been shown that the annoying allergic reaction was triggered by a specific type of hair: that of humans.

 

 

 

CAN YOU BE ALLERGIC ONLY TO MALE DOGS?

 

Introduction

In recent decades, allergic sensitization to dogs has increased significantly in “Westernized” countries, where it is common to own a pet. In these countries, the

prevalence of sensitization to dogs can exceed 20% in the atopic population

and tends to increase progressively from pediatric to adult age. Exposure to dogs in sensitized subjects can cause allergic respiratory symptoms of rhinitis and asthma, but

it can also affect the quality of life of the entire family. Avoiding exposure to dogs, by removing them from the home environment, may not be emotionally acceptable for

families who own these animals. Furthermore, it is known that dog allergens are very volatile and are transported by clothing, and can therefore also be found in public environments

where dogs are not present, such as schools and offices.

The introduction of molecular diagnostics has allowed us to better characterize the profile of

allergic sensitization to dogs. The most well-known molecular allergens of dogs are lipocalins

Can f 1, 2, 4 and 6, and serum albumin Can f 3, which are found mainly in saliva, but

also in dandruff and hair where it is deposited by licking. Can f 1 is the major allergen and is detected in the majority of patients sensitized to dogs. A new major allergen, Can f 5, has recently been

identified, to which approximately 30-60% of subjects with positive allergy tests for dogs are mono-sensitized. Can f 5 is a kallikrenia of prostatic origin, and as such is produced only in male dogs, being found mainly in urine, but also in hair and dandruff extracts. Can f 5 does not appear to cross-react with other dog allergenic molecules and its production is reduced in

sterilized male dogs. All this suggests that dog allergic subjects may react differently to male dogs compared to female dogs, depending on their molecular allergen sensitization profile. For this reason, Schoos and colleagues wanted to evaluate in a randomized, double-blind clinical study whether mono-sensitized patients to Can f 5 could tolerate the female dog.

 

The study

The study involved 22 Danish adolescents (age, 15–18 years) with allergic rhinitis (in some cases also with asthma or atopic dermatitis) and allergic sensitization to dogs, confirmed by allergy skin tests (SPT) or positive specific IgE to dog extract, regardless of history of symptoms from contact with dogs. Exclusion criteria were uncontrolled asthma, daily need for antihistamines, or history of treatment with pet immunotherapy. Participants were given SPT with both commercial dog allergen extract and specific dander extracts from male and female golden retrievers, the latter produced specifically for the study.

Specific serum IgE were also searched for both dog extract (e5) and molecular allergens Can f 1, 2, 3 and 5. Then, participants were subjected to the Conjunctival Provocation Test (CAP), instilling the extract of the allergen of a male or female dog (blinded for both the experimenter and the adolescent) in the right eye, and using the left eye as a control, and then repeating the test after a week with eyes inverted. The results showed that participants mono-sensitized to Can f 5 react to male dogs, while they seem to tolerate female specimens. Specifically, among the 7 participants mono-sensitized to Can f 5, all had positive SPT for the male dog extract, while only 1 out of 7 also had weakly positive SPT for the female dog extract (p = 0.01). Also among these 7 adolescents, 5 had a positive CAP for the male dog extract, while only 1 out of 7 had a positive CAP also for the female dog extract (p = 0.03). In contrast, participants with poly-sensitization to multiple molecular dog allergens had similar skin and eye reactions to both male and female dog extracts. Finally, in a post-hoc analysis, the authors discovered that the adolescent mono-sensitized to Can f 5, but with skin and eye reactions to both male and female dog extracts was actually positive also for the molecules Can f 4 and 6, not available at the beginning of the study, thus identifying the reason for his cross-reactions.