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Doctor insights on: What Is The Average Time Needed For An Antihistamine To Begin To Work

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What is the average time needed for an antihistamine to begin to work?

What is the average time needed for an antihistamine to begin to work?

45-90 minutes: Antihistamines taken by mouth begin to work in about an hour but may take longer if you've just eaten. Antihistamine nasal sprays (astepro, patanase) begin to work in 30 minutes. An antihistamine injection, usually diphenhydramine, sometimes given for a severe allergic reaction or anaphylaxis begins to work in a few minutes. ...Read more

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Dr. Paul Carter
601 doctors shared insights

Antihistamine (Definition)

Sedating and non-sedating antihistamines prevent and treat allergic reactions, and are ...Read more


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What is the best time to take an antihistamine?

What is the best time to take an antihistamine?

Any time: You can take antihistamines any time of the day.Take them same time of day everyday. ...Read more

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How many milligrams of antihistamine can a person take at one time?

Unclear: Different antihistamines have different potencies. 10 mg of Zyrtec is equivalent to 180mg of Allegra (fexofenadine). Mg doseage as in all medicines are drug specific. In regard to toxic levels, each has it's own known limit. However too much antihistamine can lead to deadly arrythmias/ Please use the recommended dose. ...Read more

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What is the highest dosage of antihistamine that one person can take at one time?

Antihistamines: Safety of high dose medications is often unknown. Our experience comes from case reports of persons who intentionally or accidentally consumed unusually excessive quantities. When Claritin (loratadine) was first investigated, safety studies were done at 40 mg (4 times the current recommended dose). We take 10 mg because effectiveness is not significantly different between 10 mg and 40mg. ...Read more

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I am about to take an antihistamine for the first time but my friends tell me to use it before bedtime. Will I still feel the effects the next day?

Depends on the med: Some antihistamines are more sedating than others. Medications like Benadryl (diphenhydramine) can definitely cause sedation. Newer antihistamines like Allegra and Claritin are non-sedating and Zyrtec is sedating in roughly 10-20% of patients. ...Read more

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Can i take citalopram and antihistamine at the same time?

Can i take citalopram and antihistamine at the same time?

Probably: This combination is usually safe, but individual factors may influence this. Consult your doctor to deal with your specific circumstances. ...Read more

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Do people take an antihistamine and a corticosteroid at the same time?

Do people take an antihistamine and a corticosteroid at the same time?

Yes: And the treatment should be under medical guidance, dosage of steroids need to be dictated by your treating physician. ...Read more

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Allergy shots or antihistamine pills which works better?

Allergy shots or antihistamine pills which works better?

Allergy shots: antihistamines only cover up symptoms and don't cure anything. Allergy shots treat the cause and that is why with successful immunotherapy you can get rid of antihistames. One complication of nasal allergy treated symptomatically is development of asthma. On the other hand if you treat the cause you prevent complications ...Read more