I am not disagreeing with anything posted in this thread, just adding a few cautions and throwing out some other things to think about.
Even though they seem relaxing, all Anti-histamines are heart stimulants. If you are prone to tachycardias, please be careful. I know from personal experience. Phenergan, a really strong anti-histamine, put me into abnormal heart rhythm on more than one occasion, until my doctor finally told me they are stimulants and I stopped taking it.
Anti-histamines are anti-cholinergic. We desperately need all the choline we can get to help our deteriorating memories. Lack of choline is one of the problems in Alzheimer's, not just beta amyloid plaques. At the very least, I would make sure to take a good choline supplement if taking anti-histamines a lot. Most good B Complex supps. have high dose choline.
Voluntary isolation, at least in fibromyalgia, is thought to be due to the proven low levels of human growth hormone. Somehow, this relates to the overstimulation and leads to a retreat from it. OTC Secretagogues do not work. You need injections if this is your problem, and tests to prove you have it first. Taking growth hormone when you do not need it can cause any cancers you may have to grow. It is also very expensive.
Lastly, I would urge anyone with uncontrollable anger to please get tested for Lyme Disease. My personality went from having no temper at all, to exploding for hours on end over the slightest evidence of anyone else's idiocy. Other Fibro patients I knew kept telling me it was Lyme, but I resisted until it got so bad it scared me and threatened my marriage. To my horror, two Lyme tests were positive. I have no problems with friends or anyone else I like, but we have had to put up a six foot high wood fence all the way around our property because of my run-ins with moronic neighbors. They do not realize the fence is not to protect me from them, it is to protect them from me. Lyme rage has caused several homicides. My blood pressure goes well into stroke range and stays there for days after a two minute argument with one of these types. If Lyme is the cause in your case, proper IV antibiotics for several months can help immensely. Unfortunately, I am allergic to all the ones that work on Lyme and feel certain a stroke from one of these flare ups will kill me some day soon. It is horrible to find yourself yelling and screaming, or even throwing and breaking things. Please don't assume you have to put up with this until all possibilities have been investigated.