I knew I had cat allergies but I didn't know I was going to a party where I would be exposed. Is there something I can carry in my purse in such cases? Generally my allergies aren't bad enough that I use any prescription medication.

A:  A common and effective treatment for allergies is an antihistamine. This type of medication works quickly, and a wide variety is available over the counter (without a prescription).

Doctors divide antihistamines into sedating (those that cause drowsiness, sometimes to the point of interfering with driving and interacting with alcohol) and non-sedating. The non-sedating antihistamines are newer and thus more expensive, but both are readily available.

Dr. Leslie Gimenez, an Assistant Professor of Pediatrics (Allergy and Immunology) at the Medical College of Wisconsin, recommends the non-sedating choice of generic loratadine (brand names Claritin or Alavert).

By using loratadine you would not only avoid the drowsiness seen with an antihistamine like diphenhydramine (brand name Benadryl), but loratadine lasts 24 hours instead of only 6. Dr. Gimenez notes that it would be better to take the medicine an hour before going to a home with cats, but since it does work fairly quickly, you would still get relief even after the symptoms have started.

Antihistamines work well for itching, sneezing, runny nose, and eye itchiness and tearing. If your major symptom is the nasal congestion, you might also need a decongestant like pseudoephedrine (brand name Sudafed). Dr. Gimenez recommends a combination product such as loratadine-D ("D" for decongestant).

Julie L. Mitchell, MD, MS, is an Assistant Professor of Medicine at the Medical College of Wisconsin. She practices at the Froedtert & The Medical College of Wisconsin General Internal Medicine Clinic - East. Her column appears in the Milwaukee Journal-Sentinel.