Would it be fine to take adderall with a benadryl?

Possible: Benadryl can increase the serum concentration of Adderall, because it can effect hepatic enzyme CYP2D6. However, the interaction is described as non-significant or minor. Bottom line taking a dose of Benadryl is probably not a problem. If you were going to take it regularly be aware it could effect the Adderall.

Talk 2 dr/pharmacist: There are no particular drug-drug interactions, but we don't know what other medications you are on, or what your other health issues are. Benadryl is mildly sedating and may antagonize some of the effects of adderall. An occasional benadryl for an allergic problem or insomnia is likely to be fine, while regular use of it may be a problem for you. Talk to your prescriber and/or your pharmacist.