That dose of diphenhydramine is 3 times the normal 50mg sleep-aid recommendations. This drug enters the brain, and affects histamine there too. (hence the drowsiness). Histamine in the brain is a precursor neurotransmitter, that regulates all sorts of neurotransmitter actions and release. It is also anticholinergic, and will cause urinary retention, blurred vision, and dry mouth and mucus membranes. Drying the mouth and nose too much places risk for upper respiratory infections and viruses.

I have noticed in your previous posts that you tend to overmedicate yourself by increasing doses arbitrarily. This is really dangerous and you should follow instructions on the OTC packages carefully, and also the directions on your RX labels carefully. Taking too much diphenhydramine is not wise, nor safe. The normal sleep aid dose of diphenhydramine when NOT taking ANY OTHER drowsiness producing drug (like your 2 RXs)
is 50mg. Many people can get by on 25mg if they are older in age.

http://www.drugs.com/diphenhydramine.html
overdose symptoms:
http://www.nlm.nih.gov/medlineplus/e...cle/002636.htm

Combining sedatives is a risky behavior. Please be careful.