An allergy occurs when the body has a hypersensitive reaction to allergens and produces antibodies in response to them. Because these antibodies can adhere to adipose cells (fat cells), the next time the body comes into contact with an allergen, it can activate the adipose cells and release all sorts of inflammatory mediators, such as histamines and prostaglandins, which can cause inflammation, itching, sneezing, and other allergic symptoms.
過敏疾病的發生，起源於身體對某種過敏原反應過度，產生過敏抗體，而此一過敏抗體會粘在體內的肥胖細胞上，當身體再度受到此一過敏原的刺激時，它就會把肥胖細胞活化，釋放出各種發炎物質──組織胺、前列腺素等，造成發炎反應，引起發癢、打噴嚏等過敏症狀。