Antihistamines block histamine, an inflammatory chemical released by your immune system during an allergic reaction. 

If your immune system is weak it overworks attacking everything (releasing histamines) causing allergies, inflammation and autoimmune diseases. Even my allergist doctor has it wrong, saying my immune system is too strong! I don't argue with him.

Most doctors push antihistamines, steroids and decongestants for allergies, so you have to request an allergist. I've found that allergy shots really work and they're getting more attention in the medical field. When you google it now there's a lot more info too.