6 doctors weighed in:
How long should it take for an allergy pill to work?
6 doctors weighed in

Dr. Paul Carter
Internal Medicine - Allergy & Immunology
2 doctors agree
In brief: 1/2 to 1 hour
Some antihistamines require metabolism in the liver to be converted into the most effective form to block histamine.
These antihistamines take at least 1 hour to become effective. However, some antihistamines like allegra, xyzal (levocetirizine) and Clarinex are already in the active form and begin to work as soon as they are absorbed which take about 30 minutes.

In brief: 1/2 to 1 hour
Some antihistamines require metabolism in the liver to be converted into the most effective form to block histamine.
These antihistamines take at least 1 hour to become effective. However, some antihistamines like allegra, xyzal (levocetirizine) and Clarinex are already in the active form and begin to work as soon as they are absorbed which take about 30 minutes.
Dr. Paul Carter
Dr. Paul Carter
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Dr. James Sublett
Internal Medicine - Allergy & Immunology
1 doctor agrees
In brief: About 1 hour
Most of the newer antihistamines work within the first hour of taking them. About 1/3 of people with mild to moderate allergies have some relief.
Avoidance measures are important. Allergy shots are effective in 85% of properly selected patients who have moderate to severe allergies to inhalant allergens.

In brief: About 1 hour
Most of the newer antihistamines work within the first hour of taking them. About 1/3 of people with mild to moderate allergies have some relief.
Avoidance measures are important. Allergy shots are effective in 85% of properly selected patients who have moderate to severe allergies to inhalant allergens.
Dr. James Sublett
Dr. James Sublett
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Dr. Yoram Padeh
Internal Medicine - Allergy & Immunology
In brief: 20min to 1h
Most oral antihistamines can start to take effect as early as 20 minutes and are usually in full effect by 1 hour. However, the old adage of "an ounce of prevention is worth a pound of cure" still holds true.
Taking a pill before entering an allergic environment can control symptoms better than taking a pill once the symptoms have already started. Plan ahead when possible.

In brief: 20min to 1h
Most oral antihistamines can start to take effect as early as 20 minutes and are usually in full effect by 1 hour. However, the old adage of "an ounce of prevention is worth a pound of cure" still holds true.
Taking a pill before entering an allergic environment can control symptoms better than taking a pill once the symptoms have already started. Plan ahead when possible.
Dr. Yoram Padeh
Dr. Yoram Padeh
Thank
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