Halaas said that people often confuse allergies for a cold and mistreat their symptoms. "Antihistamines are for allergies, not for congestion from a cold," Halaas said. "When fall comes around people start to sniffle, they often take the antihistamines thinking it's just an allergy kicking in but those which won't help with cold congestion. You need a decongestant that contains pseudoephedrine, but be cautious taking these if you have high blood pressure."