I'm on two controllers Singulair and Allegra and they have for the most part been great. But, when i get cold my asthma comes back. Is this unheard of? Another question concerning a cold when i take singulair is i dont have any symptoms of cold i believe due to singulair, nothing. No soar throat, headaqe, sniffles nothing. The only symptom is flared asthma, anybody else experience this? Also does singulair lower the bodies immune system because this is my 2nd cold in 3 or 4 weeks.