Sediment -- Be aware that older, more honestly or naturally made wines, throw a sediment the older the wine is. Usually in 10 years and definitely in 15 years in reds and about 25 years in whites, you should see a sediment growing at the bottom of the bottle and collecting in the area they call the punt. It is why the older the wine, the more carefully you have to handle it. With age, all the tannins, sulfites and other harsh things to fall out of the wine. It is one reason, the older the wine, the better it tastes .... to a point! Wine is like everything, it rises to an optimum point and then it inevitably declines. (See Aging in the tab marked Other Rules of Wine).
Sulfites -- Sulfites are a natural product of fermentation. Therefore, they are found in wine, yogurt, beer, vinegar etc. If you get headaches, it may not be sulfites but imbibing wines that are too young or wines that are too cheap! (Reference my comments above). At any rate, sulfites are measured in parts per million and generally a low sulfite wine will be around 35 PPM. American regulations require that American produced wine be 10ppm or less to be labeled sulfite-free. However, since sulfite levels fall off with age and the wine is tested at time of bottling .... well....you be the judge of what you can tolerate and afford!
Reserveratrol, Reserveratrol, Reserveratrol? -- It is my "Marcia, Marcia, Marcia" moment from the wine business. Reserveratrol belongs to a class of compounds called polyphenols (anti-oxidants) which are present in wines. Yes, they are good for you but there is debate about how much is present in a glass or two, or how much good that glass or two will do in the grand scheme of things. There are claims you would have to drink a barrel or two to have any appreciative impact. I discovered reserveratrol in the mid eighties. A health expert who spoke at a national sales meeting in the 90's "pooh poohed" my question about reserveratrol which implied the compound had health benefits. At one point it was given as an explanation for The French Paradox: how the French lived so long despite and diet heavy in fats and lack of exercise. I leave it to you to decide but I must add I have never heard any one claim it is bad for you!
Tannin, Ketones and other Young Stuff -- Just as all things young tend to greater aggression and strength than the aged, certain young wines based on grapes full of tannin, such as the Cabernet Sauvignon grape from Bordeaux, will repeat this pattern . Tannin, for example, is found in vegetative matter and gives young wine, and strong tea for that matter, a puckering astringency you sense at the back of your palate. This tannin, along with ketones, color pigments and other things from the grape skins and seeds can dissipate and/or drop into the sediment with age, but when the wine is young, they remain for you to drink. They also contribute to dehydration, so beware of youth... but they fall away with age!
Water and Wine -- A good rule of thumb, especially when drinking young wine, is to have a glass of water for every glass of wine you consume. Dehydration minimally could lead to a headache the day after!
White versus Red Wine -- Generally, white dehydrates less than red due to the more powerful elements coming out of the skins of red grapes. The exception to this is a sweet wine such as Sauternes since its heavy sugar content further dehydrates. Keep in mind, however, that a cheap white, with lots of residual sugar/fructose to hide the quality, will likely be more trouble to your body than a quality, aged red. Just as some restaurants add sugar to avoid cooking a tomato sauce all day to "sweeten" it, there is a similar quality shortcut in winemaking in leaving behind a lot of grape sugar! Again, excluding well made, intentionally sweet, late harvest wines such as Sauternes, the rule is that the drier the wine, the better the bottle.
White before Red? You may drink white before red with little peril but watch out for white after drinking red (regarding beer, the rule is never wine before beer but many tolerate beer before wine).
Wine and Dehydration
People often ask me "How do you tell a good from a bad wine?' I reply, "The next day!" Good wine should not give you a headache if you exercise care. Anything which dehydrates apparently increases some people's tendency to such things as headaches or a feeling of seasickness and all alcoholic beverages dehydrate. Absolutely avoid foods and beverages that put your stomach on edge and increase a tendency to dehydration. Below are certain generalizations about wine which you may follow to help avoid problems.