Why do the majority of allergy relief medicines contain things that put you to sleep?

Benadryl (diphenhydramine): Most allergy medications are anti-histamines. Older ones like Benadryl (diphenhydramine) easily cross into the brain and block histamine. Histamine in the brain is a wake promoting neuro-transmitter. Histamine in the skin, lungs, causes typical allergy symptoms. Newer generation anti-histamines (claritin, allegra) do not cross as easily into the brain and are not usually associated with sleepiness although all can.

Not true: While the older anti-histamines crossed into the brain and caused sedation, newer antihistamines like claritin(loratidine and allegra(fexafenadine) do not cross into the brain and only very rarely cause sedation. These medications are also available over-the -counter and the generic forms are very cost effective. Try them and i doubt you will be sedated especially if taken in the evening.