Freezing winter temperatures actually help most seasonal allergy and asthma sufferers in a few ways, and for the most part, this winter has not brought these benefits.
Cold temps bring relief from those who suffer from pollinating plants and trees. - Colder temperatures drive pollen producers into a winter hibernation, but warmer temps mean some trees and plants are already budding.
Lower temperatures and/or snowfall holds outdoor molds in check. - As noted in a previous about mold allergies and fall, warmer temperatures can mean an uptick in mold spores from dead and decaying leaves.
Lastly, asthma sufferers are particularly sensitive to temperature/barometric pressure swings. - When temperatures spike and dip, as is common during the fall, asthma sufferers typically see an increase in symptoms, like wheezing, coughing and nasal swelling. Steady temps, warm or cold, minimize this.
For non allergy sufferers out there, don't think you're in the clear. Warmer winters typically signal a good year for insects, which is usually only good news for... insects.
So while I may think it's nice to see that the daffodils and tulips in my back yard have already sprouted, the fact that they did so in January probably doesn't make them as welcomed a sight for allergy or asthma sufferers.