No. Not any more often than in the general population.
Yes. Yes indeed, the mechanism behind "common allergies" is very different from what happens in alopecia areata.
No. Not more than with other people. I do not recall an increased incidence of allergy in patients with alopecia areata.
Not specifically. Asthma and allergies are what are called atopic diseases which are hypersensitivity reactions in various parts of the body (asthma - lungs, allergies - mucosal membranes) due to various triggers like viruses, allergies, pollution, etc., whereas alopecia areata is an autoimmune disorder where the body's immune system attacks the hair follicles for reasons that are not clear. Read more...