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Antihistamines: What You Need to Know

Whether by prescription or purchased over the counter at any drugstore or supermarket, antihistamine medications are an effective way to keep hay fever reactions at bay and make allergy season a little more tolerable. As the name implies, antihistamines work by blocking the action of histamine, a chemical released by the body in response to an allergen. Histamine can cause sneezing, runny nose, itchy eyes or skin, or hives. Here's what you need to know about taking antihistamines.

Make It A Routine

If your doctor advises that you go the antihistamine route, take your medicine regularly during an allergy season to prevent hay fever problems. On-and-off use of antihistamines may result in more noticeable side effects and less effective control of your symptoms.

Time It Right

If you are taking an antihistamine that makes you drowsy, it is reasonable to take the medication about a half-hour before going to bed. More recently developed antihistamines (marketed as “non-sedating” antihistamines) cause drowsiness in a smaller number of users. If these are easier for you to take without drowsiness, they may be worth it. If you are not using a 24-hour medicine, you may help to keep costs down if you use inexpensive sedating drugs at night and take the non-drowsy version in the morning.

Build Up Gradually

Although some antihistamines such as Claritin and Allegra relieve hay fever symptoms for most people without the common side effect of drowsiness, other prescription and over-the-counter medications frequently cause daytime sleepiness or, less commonly, restless nights. To avoid these problems, your body needs to get used to the medication gradually. Start by taking pills only at night. If your brand suggests taking two pills in a 24-hour period, begin by taking a single nighttime dose for three days. Starting on the fourth day, you can take one pill at night and one in the morning. If you are using a medication you are directed to take several times a day, you may similarly want to start slowly, but gradually build up to the recommended dosage after several days.

Try Different Brands

People react differently to different medications, so if one over-the-counter brand consistently makes you drowsy or causes other side effects (such as dry mouth or nausea), try another. If you're taking a prescription antihistamine, ask your doctor for a substitute. If your symptoms are just nasal, inhaled nasal corticosteroids (such as Rhinocort, Nasacort, Beconase and others) are better than antihistamines in relieving a runny, itchy or stuffy nose.

Be Conscious of Side Effects

Antihistamines are not right for everyone. They can be hazardous for some people, particularly those who are elderly, those who have dementia or a tendency to become confused, or those who are prone to falls. Many people are aware that antihistamines can result in drowsiness, but in children and some older individuals, they sometimes have the opposite effect, causing agitation or hyperactive behavior. Antihistamines can also cause a dry mouth, cause constipation, or result in incomplete emptying of the bladder. (This last problem, called urinary retention, can be a particular problem for a person who has frequent bladder infections or a person who already experiences a delay when beginning to urinate.) Although not all brands have been studied formally, an increased rate of automobile accidents has been recorded in people who have taken antihistamines.

Some antihistamine brands are packaged together with a decongestant medication. An example of this would be Claritin-D, which combines the antihistamine loratadine (Claritin) with pseudoephedrine, a decongestant. Decongestant ingredients may cause side effects such as heart racing, high blood pressure, or insomnia, so you may wish to avoid a combination product if you are sensitive to these side effects.