# Benadryl effective time **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [September 4, 2024, 1:39pm UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747 "2024-09-04T13:39:26Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [September 4, 2024, 1:39pm UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747/1 "2024-09-04T13:39:26Z")
A few months ago I started having problems with itching. It always starts with the top of my right ear, then my eyes, then it will start jumping all over my body where everything itches. The Benadryl gives my fast effective relief. My question is that it seems to last for about 4 days before I need another one. The effectiveness of Benadryl is supposed to last about 4 hours. Is it possible that whatever is causing the itch might be extremely sensitive to very small amounts of the drug. The half-life is listed at about 4 hours. I should add that I get a normal reaction to the allergy type relieving benefits such as stuffy nose which I normally just put up with. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 4, 2024, 1:56pm UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747/2 "2024-09-04T13:56:33Z")
It all depends on what is causing the itching. I don’t have any serious allergies but my theory is the effects of minor allergies compound. Spring and summer give me traditional hay fever, watery highs, a scratchy throat, various itches. If I had in spices I’m sensitive to and shrimp which gets me a little itchy it gets worse. If I take a Benadryl everything calms down and maybe my body is better able to deal with the histamine reactions for a while. YMMV ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [September 4, 2024, 2:03pm UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747/3 "2024-09-04T14:03:35Z")
> [@TriPolar](#): > > It all depends on what is causing the itching. I have a suspicion. I don’t normally get bit by fleas or mosquitos, but lately I have been experiencing some kind of a bite that creates a large painful welt. Hot water instantly removes it but I am wondering if that is what is causing my full body itches. ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [September 4, 2024, 2:17pm UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747/4 "2024-09-04T14:17:44Z")
> [@HoneyBadgerDC](#): > > it seems to last for about 4 days before I need another one. If the itching starts and you do not take diphenhydramine will the itching eventually go away? If so, does it stay away for 4 days? ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [September 4, 2024, 2:24pm UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747/5 "2024-09-04T14:24:48Z")
Pain and itching are sensations that involve a lot of psychological feedback in addition to physical inputs. It could be that your itching sensation was 20% physical and 80% psychological, and after suppressing the physical part for a few hours, then the psychological feedback is likewise diminished. This is what my physical therapist said about pain, that a good part of physical therapy is not actually physical intervention like stretching the muscle, but “distracting” the pain fibers by putting them through different patterns of sensation and motion. After doing that a few weeks, this disrupts the pain cycle without actually making much physical change on the thing that was hurting. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [September 4, 2024, 2:31pm UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747/6 "2024-09-04T14:31:02Z")
> [@kayaker](#): > > If the itching starts and you do not take diphenhydramine will the itching eventually go away? If so, does it stay away for 4 day This is a good question. I am not sure but it does seem to come and go every day if I am recalling right. It becomes so severe not that I can’t delay taking the pill to check it out. > [@HMS\_Irruncible](#): > > This is what my physical therapist said about pain, that a good part of physical therapy is not actually physical intervention like stretching the muscle, but “distracting” the pain fibers by putting them through different patterns of sensation and motion. After doing that a few weeks, this disrupts the pain cycle without actually making much physical change on the thing that was hurting. This is interesting as I have noticed different phycological issues will trigger an itch. Very possible that just interupting it is what is happening. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 4, 2024, 2:43pm UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747/7 "2024-09-04T14:43:29Z")
> [@HoneyBadgerDC](#): > > This is interesting as I have noticed different phycological issues will trigger an itch. Very possible that just interupting it is what is happening. Sometimes scratching itches makes me itchier. When it doesn’t then the itch has some more obvious cause, a bit of dry skin, something stuck to my skin, a minor scratch, even the bump from a mosquito bite. Those are things actually removed by scratching the itch. More general itchiness tends to spread from scratching for me. Enough scratching and I think the source of the itching is now secondary to the minor but real pain of skin scratched raw, which can be a relief in itself. ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [September 6, 2024, 3:06am UTC](https://boards.straightdope.com/t/benadryl-effective-time/1006747/8 "2024-09-06T03:06:41Z")
It may not be external at all… Lots of dementia patients have itching and picking episodes. Get checked out by a neurologist. Just to make sure.