An allergy is an extreme reaction of the immune system to harmless stimuli like animal hair or pollen. It can occur at different ages, some begin in early childhood, others appear at grownups. Different factors are said to be possible reasons for allergies. So a low-gearm childhood could be a reason, because the immune sytem doesn’t learn to decide between danger and non-dangerous stimuli.
Another important factor is the gut flora. Under influence of antibiotics or other factors it does not develop correctly and so the immune system gets a deficit which acould lead to allergic reactions. There are several of those possible reasons.
If you want your allergy to be treated complementary I could offer you a detailed one hour anamnesis in my office to start with and an individual Diagnose- and therapy plan.