Allergy and hypersensitivity

WELLNEWS

Victor Romulo Gallardo Dumaguing, MD

The fear of allergy is one of the identified reasons for the vaccine hesitancy of some sectors of society. Add to that the concerted effort of anti-vaxxers who have used trimedia outlets- TV, radio, print- in denouncing the vaccination roll out of the government, with some even proclaiming that the vaccines are more deadly than the Covid 19 virus itself. Sad memories linger especially in the minds of those bereaved by the demise of their loved ones allegedly due to the Dengvaxia vaccine
    The vaccines which currently have EUA- emergency use authorizations- have either polysorbate or polyethylene glycol as preservatives which have the potential of inducing allergic reaction in some patients. It must be emphasized that allergy runs in families, in the same way as bronchial asthma, atopic dermatitis, eczema, allergic rhinitis, hay fever. Persons with the above ailments share in the common a high level of the immunoglobulin E (IgE) and eosinophil, one of the white blood cells.
    At this juncture, it would be good to differentiate allergy from hypersensitivity, two words which are often considered as synonymous; they may be related but not similar. Allergic reactions occur in a person who has had PREVIOUS exposure to the allergen which acts as antigen. Example is someone who develops signs and symptoms of allergy to quail eggs, when in fact, he/she has been eating chicken eggs.
    Hypersensitivity is a FIRST-TIME exposure to an antigen or allergen, the amount of which may be small or in big amounts. Incidentally, we develop allergy to the PROTEIN content of our food like eggs, meat, fish, milk, beans. Some allergologists simplify by saying, “avoid things that crawl and fly” with obvious reference to shrimps, crabs and of course, chicken
    From a clinical standpoint, allergic or hypersensitivity reactions are classified as mild, moderate and severe, with all of them having something in common. Majority of allergic manifestations is the effect of HISTAMINE, which is secreted by connective tissue cells called Mast cells. Histamine, along with other mediators like kinins, SRSA- slow reacting substance for anaphylaxis, induce massive vasodilatation or loosening of the walls of blood vessels especially the arteries and capillaries.
Thankfully 80 % of allergic reactions are mild, with rashes or erythema as most common, followed by pruritus or itchiness. Urticaria and hives ( pamamantal in Filipino, supot-supot in Ilokano are also usual findings. These signs and symptoms fortunately are, for the most part, not serious, although they could be bothersome. Anti-histaminics bought over-the-counter provide relief and comfort.
    Diphenhydramine and Chlorphenamine are very popular; they belong to sedating antihistaminics so-called because they induce drowsiness, thus, not given to people who drive to work, those who operate heavy machineries and related activities which require alertness and snappy attention. The sleepiness is welcomed by mothers whose kids suffering from allergic reaction are somehow prevented from vigorously scratching those itchy lesions which could lead to infection. Nowadays, the non-sedating antihistaminics, example Cetirizine, Loratadine, to name a few, are favored by employees who have the usual 8am-5pm work schedule. Plus the convenience of once-a-day dosing.
    An allergic reaction is considered moderate, if aside from the cutaneous or skin manifestations, there are now gastrointestinal symptoms as exemplified by patients stung by jellyfish, in which there is nausea, vomiting with abdominal pain. 15% of allergic reactions are of the moderate type, which can be ameliorated by injection of anti-histaminics. At this point, it is not wise to drench the stung area with urine or dab it with toothpaste, as some onlookers are wont to do.
    ANAPHYLAXIS is the most serious, and potentially fatal result of allergy. It includes anaphylactic shock with worrisome cardiopulmonary symptoms; sudden drop in blood pressure, dyspnea or difficulty in breathing. This requires IMMEDIATE hospital or clinic intervention. That explains why, for people who have experienced severe allergic reactions, they have a handy Epinephrine injectable, just in case. As an addendum, medicines like Penicillins and their derivatives, and aspirin are known to be allergenic, so patients are encouraged to volunteer their allergy history to their health care providers. As nothing can beat Peanuts among the nuts when it comes to allergy. Stay Safe always.