Is it a drug allergy or just a side effect?

Medication reactions are not always an allergy.  For example, many antibiotics will lead to non-allergic side effects, such as stomach upset or yeast infections.  This is due to irritation of the stomach or killing off of "good bacteria" as well as the bad -- leading to overgrowth of yeast and other organisms that normally are kept under check.

True allergy to a medication is an immune reaction to the drug, leading to release of histamine that can cause anything from mild to severe hives, swelling of the eyelids, lips, mouth, or throat, breathing difficulty, or life-threatening anaphylaxis.  Symptoms of a drug allergy can range from mild to life-threatening.  Once a drug allergy has occurred, it is important to let your doctors know, so that this drug can be avoided as a treatment option in the future.

Can you lose allergies to foods?

If you have been found to have an allergy to a food such as milk or wheat by skin test or blood test (specific IgE antibody), and eating that food leads to hives, swelling, itchiness, diarrhea, or wheezing, you will of course be advised to avoid that food. But in many cases, after staying completely away from it for 6-12 months (longer if extremely allergic), you may eventually lose the hypersensitivity to that food and will again be able to safely eat it. Recent studies show that this may be due to down-regulation of receptors over time. This rule does not tend to apply to severe allergy to peanut, nuts, or seafood -- these tend to last a lifetime; only 1 in 5 children with peanut allergy will "outgrow" it.

Chronic hives may be effectively treated with high dose Xyzal or Clarinex

Chronic urticaria, or “hives”, can be very bothersome and may not improve with usual doses of antihistamines used for other conditions (e.g., nasal allergies). Patients often ask whether it would be safe and helpful to take 2-3 times the usual doses of antihistamines such as Clarinex or Xyzal. In a recent study, increasing the dose of Xyzal from the usual 5 mg up to 20 mg per day did result in markedly improved control of hives. Increasing Clarinex similarly was also moderately helpful. There was no increase in drowsiness or any other side effect with either medication. So, it may be safe to take higher doses of these medications when needed for severe chronic hives, though we would recommend starting with lower doses and increasing only if approved by your doctor.

J Allergy Clin Immunol 2010;125:676-82. The effectiveness of levocetirizine and desloratidine in up to 4 times conventional doses in difficult-to-treat urticaria. Staevska M, Popov TA, Kralimarkova T, Lazarova C, Kraeva S, Popova D, Church DS, Dimitrov V, Church MK (Bulgaria, UK, Germany)

Chronic Hives and High Blood Pressure

A recent study found that the duration of hives was significantly longer in patients with high blood pressure that is not adequately controlled. This finding had nothing to do with the medications being used to treat hypertension. It has not yet been determined whether or not adequate treatment of high blood pressure will result in improved management of hives.

Take home message: For those patients who have chronic hives and are also being treated for high blood pressure, check with your family doctor to see if your hypertension is well controlled.