The use of H1 receptor blockers including Zyrtec and Clartyne are first line treatments for allergies including food allergies. They block the histamine mediated effects including the rash, itch and some respiratory effects.
Stomach acid release is mediated by histamine binding to H2 receptors. H2 antagonists (blockers) include ranitidine and famotidine. There is some evidence that H2 antagonists may help with the late, second stage, or relapse effects in severe allergy but they are not recommended as main line treatment for allergy. Similarly corticosteroids are used in anaphylaxis but as a second line measure to prevent late responses.
The problem with the regular use of H1 blockers is the patient may miss the first signs that they have ingested an allergen and consume more of the product so have a higher allergen load on board when symptoms appear. It's just something to be aware of.
Allergies develop at all stages of life. Unfortunately patients can develop allergies to medications which have previously been safely used and respond with anaphylaxis on later doses. Allergy can be severe at any time not just in childhood.
Food allergies can also develop later in life due to cross reactivity in similar shaped molecules in other products. Latex allergy is linked to food allergies due to cross reactivity with food triggers including kiwi fruit, banana, chest nuts and avocado.
First line treatment for all allergy is antihistamines then epinephrine given as soon as severe allergy manifests. Other treatment includes IV fluids and occasionally glucagon if patients are on beta blockers as they block epinephrines effects.
