Antihistamines or Decongestants? Getting Allergy Relief

While there is no quick fix for your runny or congested nose, antihistamines and decongestants continue to be some of the most widely used medicines for allergy relief.

But how do you know if an antihistamine or a decongestant will give you allergy relief? Who should use these allergy relief medicines -- and who should avoid them?

Why are antihistamines used for allergy relief?

Allergies occur when the body’s immune cells release a chemical called histamine in response to contact with an allergen. Histamine is one of the chemicals that causes swelling of the membranes in the nose and increases mucus.

When histamine is released during an allergic reaction, you may have symptoms such as a runny nose, sneezing, swollen nasal passages, weepy eyes, and nasal stuffiness.

While antihistamines cannot cure your allergy symptoms, they do block the effect of histamine and give you some allergy relief.  Antihistamines help relieve such miserable symptoms as sneezing, itching, and nasal discharge. They may also help relieve nasal congestion, and skin and eye symptoms.

Your doctor may prescribe short-acting antihistamines, which are taken every four to six hours. There are also timed-release antihistamines that you can take every 12 or 24 hours.

When should antihistamines be taken for allergy relief?

Antihistamines work best if taken before you feel allergy symptoms. If taken regularly, antihistamines can build up in the blood to give a protective effect against allergens and the release of histamines.

What are the common side effects of antihistamines?

The most common side effects of the older first generation antihistamines such as diphenhydramine (Benadryl) and chlorpheniramine (Chloratrimeton) are sedation, drowsiness, and dry mouth. If you take these sedating antihistamines, you may want to use them at night before bedtime to avoid feeling tired the next day.

The newer second-generation antihistamines such as loratadine (Claritin), fexofenadine (Allegra), and certirizine (Zyrtec) are less likely to cause drowsiness and can be taken during the daytime.

When are decongestants beneficial for allergy relief?

If you live with constantly swollen nasal passages from allergies, decongestants may give you allergy relief.

Decongestants reduce nasal congestion and other allergy symptoms by constricting the blood vessels and decreasing the amount of fluid that leaks out into the lining of the nose. Oral nasal decongestants come in many forms, such as pills, tablets, liquids, or nasal sprays.

Commonly used decongestants include pseudoephedrine and phenylephrine. These decongestants work in the same way to reduce swelling and congestion. These agents may be found alone or more frequently in combination with other medications such as antihistamines.

What are side effects of decongestants?

Decongestants can cause nervousness, sleeplessness, and increased heart rate and blood pressure. If you use decongestant nasal sprays for more than three or four days in a row, they may also cause rebound rhinitis. Rebound rhinitis results in increased nasal congestion and swelling.  

Are there combination medicines for allergy relief?

Combination medicines are also available for allergy relief. For instance, loratadine (Claritin) and pseudoephedrine (Sudafed) are combined in the over-the-counter product Claritin-D. This allergy relief medicine gives the benefit of the antihistamine to prevent nasal allergies and the decongestant to open swollen nasal passages.

While antihistamines and decongestants are popular allergy relief medications, inhaled steroid nasal sprays are currently the most effective maintenance therapy for allergic rhinitis (allergies) and cause few side effects at the recommended doses. These inhaled steroid sprays are particularly effective in the treatment of nasal congestion.