Causes of headaches: Solvents and Other Chemicals
Solvents come in many forms. Most are based on petrochemicals (chemicals with a petroleum base) and are used as cleaning agents, as paint thinners, or in glues, etc. While solvents are usually harmless in small quantities, those working with the same solvents day in and day out may become allergic to them, and where there is a massive amount liberated (for example, in a car-spraying plant) good ventilation is essential. Similar problems occur with 'carrier chemicals' used in the home - wax polish sprays, and pressurised aerosols as well as dry cleaning fluid, glues, deodorants, perfumes, and chemicals used in hairdressing salons (i.e., permanent waves and bleaches). In addition, chemicals exude from paintwork, artificial fibres (especially fresh carpets), and plastics.
Usually it's easy to show a relationship between exposure to the solvent and the headache. A headache that only begins at work may well be related to some chemical to which you are being exposed in the workplace. However, exposure at home can be more difficult to sort out. Constant low-dose exposure, especially with an allergy, can be difficult, because you may not be away from home for long enough to clear the chemical to which you are sensitive out of your system. Consider allergies as a cause if your headache goes away when you're away from home for a few days, and returns when you return.
However, things are not always as simple as this, because the headaches may be related to family stress, which is absent when you're away on business; or to the poor quality of your bed. Nevertheless, patiently working through the possibilities, eliminating suspect items one by one and putting them back in again after a few days may tell you what is going on quite quickly. From then on it's a matter of eliminating those things that seem to cause you problems.
Perhaps the most difficult situation is that of the worker who gradually becomes sensitive to solvents and chemicals he uses. A typical; example is the professional painter who's become sensitive to solvents in paint, Constant low-dose exposure, even in well-ventilated rooms, will be enough to give him headaches, often apparently at random. Other groups who experience chemical sensitivities at work include those working directly with chemicals - in the photographic industry or the pharmaceutical and petrochemical industries, for example.
There is no real treatment for solvent-related headaches other than excluding them from your environment. If you are getting pharmacological-type problems (dose-related), simply installing proper ventilation hoods and extractor fans may be all that's necessary; but, if you are developing a true allergy, you may even need to change jobs. Homoeopathic desensitisation might just work.
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Causes of headaches: Food, Chemicals, Drugs, Additives and Alcohol

Causes of headaches: Gas

Car Fumes