Is taking one Benadryl every night for 4 years harmful? What are the long-term side effects?

I take it because for years I've had inner ear fluid build-up. One Benadryl per night seems to be enough to keep the ears dry & the resulting nausea at bay. I must admit that I'm not sure this is still even a problem for me. The last time I stopped to see if I still needed it was about 2 years ago. After 3 days, the dizziness/nausea/inner ear issues came back, so I promptly started taking the nightly Benadryl and all has been well since. I'm going to stop again to see if I still need it. I suppose I should see an ear specialist, but Benadryl is a cheap quick fix, so I've been using it.

I have Meniers Disease, I know about fluid build up in the inner ear. I have suffered since 1995, It is a bad situation. You need to resolve the water problem in your body. Yes, it may come back but very seldom you will have the problem. Cut out salt in your meals. Salt sub. is nasty, so I use herbs. The other day I made mashed potatoes and yes, you should have salt or herbs in it. I added hazelnut cremora, wow it added a sweet and a wonderful taste without the salt. Salt is for flavor, I just changed the rules of cooking.
Hope this all helps.

Thank you so much! Your advice is just what I needed to know. I have always retained water & have had high blood pressure. However, 6 weeks ago I started a healthier diet & have drastically reduced the sodium in my diet, along with eating healthier in general. Because of this, my blood pressure is now slightly below normal every time I take it and I've even been cutting my blood pressure prescription pills in half for over a month - still getting the low readings. I didn't know that the ear fluid was related to water retention. I'll bet I can quit taking the Benadryl and the ear fluid will not be an issue any longer, since I've gotten rid of the water retention/sodium problem. This is good news. I'm stopping the Benadryl now to see if I'll be OK without it. Thank you again. It makes sense that the inner ear fluid issue WOULD be related to water retention in general, but I just never put 2 and 2 together.

Ménière's: The fluid builds up on the little hair folicles in the inner ear. Now this is what causes an imbalance, dizziness etc. Till it is all straighten out do not try the rides at Disneyland. Or go on a boat or flying use benedryl or antivert before you go.
The most research that has been done on this subject is at the House Ear Clinic in Los Angeles, CA, Dr. Slattery. Doctors from all over the world study there,
I hope this helps.