# Can common side-effects develop at any time? **URL:** \ **Category:** Factual Questions\ **Created:** [August 24, 2010, 6:59pm UTC](https://boards.straightdope.com/t/can-common-side-effects-develop-at-any-time/551322 "2010-08-24T18:59:47Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![wonky](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wonky/32/393_2.png) [@wonky](https://boards.straightdope.com/u/wonky)\ **Post date:** [August 24, 2010, 6:59pm UTC](https://boards.straightdope.com/t/can-common-side-effects-develop-at-any-time/551322/1 "2010-08-24T18:59:47Z")
I have terrible allergies, so I end up taking a lot of Benadryl. Benadryl doesn’t make me drowsy, which seems to be an unusual reaction. In fact, I will occasionally have trouble sleeping if I take it too late at night.\* But I’m wary about taking it during the day or before driving just in case it does start making me drowsy. Do things like this happen? Can a drug’s common side-effect pop up even if you have never had a problem before? Or can I count on Benadryl not making me drowsy? \*I have had this reaction to all medications I’ve ever had with sedating properties. I don’t know if it’s a coincidence or I’m just weird. Anti-depressants, on the other hand, send me to sleep like crazy. ---
**Author:** ![billy](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@billy](https://boards.straightdope.com/u/billy)\ **Post date:** [August 24, 2010, 7:23pm UTC](https://boards.straightdope.com/t/can-common-side-effects-develop-at-any-time/551322/2 "2010-08-24T19:23:22Z")
> [@jsgoddess](#): > > Do things like this happen? IANAD, but yes. People change and their reactions to meds change over time as well. No sites, just personal experience. I used to be able to use Advil-PM to put me soundly to sleep. Then I quite using it for several months. Now if I use it, it is as likely to give me RLS as it is to make me sleep. Allergies suck. Luckily I have few.