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A member asked:

what are long term side effects of diphenhydramine antihistamines and do they lose effectiveness over time? k

1 doctor answer1 doctor weighed in
Dr. Michael Zacharisen
Allergy and Immunology 33 years experience
Minimal: Diphenhydramine is the active ingredient in Benadryl (diphenhydramine) and has been around for a very long time. Like most antihistamines, there is not believed to be long term side effects. Losing effectiveness is less well studied, but with ongoing use there could be some development of tolerance or it could be that you are still being exposed to an allergen and that is why symptoms are not controlled.

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Similar questions

A member asked:

Can I take Benadryl (diphenhydramine) while breastfeeding?

2 doctor answers2 doctors weighed in
Dr. Marc Grella
Pediatrics 28 years experience
Yes: Taking Benadryl (diphenhydramine) can lead to a temporary decrease in breastmilk supply but usually it is minor unless you take a lot or for a long time.
A 45-year-old member asked:

Is it safe to take Benadryl (diphenhydramine) while pregnant?

2 doctor answers2 doctors weighed in
Dr. Megan Bird
Obstetrics and Gynecology 19 years experience
Yes: Benadryl (diphenhydramine) is considered safe in pregnancy. Some people take it for congestion or allergies. It can make folks sleepy however. If you have trouble sleeping, Benadryl (diphenhydramine) may be a big help.
A 41-year-old member asked:

For what length of time will antihistamines remain active in the body?

2 doctor answers5 doctors weighed in
Dr. Giana Nicoara
Allergy and Immunology 28 years experience
Depends: It depends on a few factors including the rate at which the antihistamine is metabolized by a particular person, other concommitant medications which can affect the rate at which it is metabolized, age of the person, and whether an antihistamine is long acting( like zyrtec) or short acting(like benadryl).
CA
A 37-year-old member asked:

Can you Claritin and Benadryl (diphenhydramine) be taken together?

3 doctor answers4 doctors weighed in
Dr. Michael P Vaughn
Allergy and Immunology 34 years experience
Yes: Most antihistamines are dosed at levels much below the toxic levels. Claritin was initially tested in drug studies at 4 times the current recommended dose. These same studies found that 10 mg yielded nearly equvalent effects as 40 mg. Since there is not a dramatic dose effect, increasing to higher levels rarely improves nasal symptoms. Benadryl (diphenhydramine) may have drying effects but sedation limits the dose.
A 34-year-old member asked:

Do Benadryl (diphenhydramine) and Adderall interact with each other?

2 doctor answers10 doctors weighed in
Dr. Michael P Vaughn
Allergy and Immunology 34 years experience
Drug interactions.: Benadryl (diphenhydramine) can be sedating (typically) or stimulating (unusual) . When a reaction occurs opposite to what is typically experienced, it is called a paradoxical reaction. A pharmacist can run a drug interaction screen for you and this is why it is wise to get all of your medications from a single source. Decongestants are stimulants and often used in combination with Benadryl (diphenhydramine) and could be a bad mix.

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Last updated Dec 30, 2016
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