Since allergies are caused by an overactive immune system, and people with AIDS have compromised immune systems, do people with AIDS not get allergies?
Yep, they do. So do people on immune suppressing drugs after transplant, and people on highdose steroids for lupus exacerbations or asthma (although their reactions are lessened because of the nature of steroids).
The problem is the immune system comes in five subsets. (Karl Gauss et al can probably break it into a hundred and five subsets.) Allergies are caused by overactivity in only one part, and that part happens to be made up of a tight stimulus-response loop that is very hard to break. AIDS knocks out a different part entirely. So do immune suppressant drugs. This is why people with AIDS get such weird diseases like PCP, instead of coming down with every disease under the sun like the bubble boy. They still have the other four parts of their immune system functioning though their T-helper cells are knocked out. They still make antibodies to strep and staph infections.
If histamine is the molecule responsible for the itching and swelling of a mosquito bite, why do people on antihistamines still know it when a mosquito bites them? Same idea. (Not an exact analogy, but illustrative)