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.
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.
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.
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.
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.