I'm an asthmatic and have been since very young. Also, in the last few years I've been getting hayfever for about 7 months a year. So far (touch wood) neither dses have shown any signs (although we worried for a bit that ds1 had it when he was 2, but it turned out to be a succession of unrelated chest infections followed by croup!)
Ds2 shows some sign of the occasional skin allergy (one to a mix of suntan lotions - we weren't aware nursery were using one as well as us, one to a recent mystery substance we think we've traced to a brand of soap flakes nursery were using for an art project) but other than that they seem to have escaped my auto-immune deficiencies, thankfully.