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A 23-year-old male asked:

is there such thing as antihistamine resistance? seems like it becomes less effective the more i take it.

2 doctor answers2 doctors weighed in
Dr. Michael Fisher
Dermatology 32 years experience
Drug Resistance: Tachyphylaxis: Rapidly decreasing response to a drug or physiologically active agent after administration of a few doses. Try a different antihistamine and that should work for you.
Dr. David Voron
Dermatology 51 years experience
Possibly: Occasionally this happens. Stopping the antihistamine for a few days, and then switching to a new one may help.

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Similar questions

A 30-year-old member asked:

Is there an over-the-counter antihistamine medication available to treat poison oak?

2 doctor answers3 doctors weighed in
Dr. Barbara Stark Baxter
Allergy and Immunology 42 years experience
Steroids needed: If you have a significant case of poison oak, antihistamines are unlikely to faze the itching. You probably need oral steroids. You can certainly try oral antihistamines and topical steroids like cortisone 10, but these rarely control the severe itch of even a moderate case. Better see your doctor for stronger stuff. Most cases last about 3 weeks.
A 38-year-old member asked:

What is the difference between first and second-generation antihistamines?

3 doctor answers5 doctors weighed in
Dr. Stephen Kimura
Allergy and Immunology 35 years experience
Side effects: The second generation antihistamines were developed to try and decrease the side effects of the first generations. Many are "purified" first generation antihistamines so they have the active effects without the side effects of drowsiness, sedation, dry mouth etc. They also tend to have longer half lives, meaning they can be taken once or twice a day not every 4 hours.
A 39-year-old member asked:

Are there any prescription antihistamines?

2 doctor answers12 doctors weighed in
Dr. Alex Martinez
Specializes in Allergy
A few: Antihistamines have been around for many years & many that used to be prescription are now available over-the-counter. A few antihistamines are still prescription, including some first-generation (sedating) medicines like periactin or palgic as well as second-generation (less-sedating) medicines like xyzal (levocetirizine) and clarinex.
Dr. Maziar Rezvani
Allergy and Immunology 21 years experience
Hydroxyzine is still prescription as well
Nov 23, 2011
Dr. Paul Carter
A Verified Doctor commented
A US doctor answered Learn more
Many prescription medications have antihistamine properties. Talk to your personal physician about which medications are right for you.
Jan 1, 2012
A 34-year-old member asked:

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

2 doctor answers7 doctors weighed in
Dr. Michael P Vaughn
Allergy and Immunology 34 years experience
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.
A 35-year-old member asked:

Which antimalarial drugs are used in areas that have multiple drug resistance?

1 doctor answer1 doctor weighed in
Dr. Martin Raff
Infectious Disease 56 years experience
Complicated: This depends upon which area of the world and to which drugs the parasite has become resistant. Check the cdc website for the state of the region in which you are interested and the drugs currently being recommended.

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Last updated Jun 10, 2014

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