Persons addicted to the excessive use of tea, coffee, alcohol, and tobacco are often subject to headache from poisoning of the system by these substances. In tea, coffee, and tobacco poisoning there is also palpitation of the heart in many cases; that is, the patient is conscious of his heart beating, irregularly and violently (see Palpitation), which causes alarm and distress. Cessation of the habit and sodium bromide, twenty grains three times daily, dissolved in water, administered for not more than three days, may relieve the headache and other trouble.

Many drugs occasion headache, as quinine, salicylates, nitroglycerin, and some forms of iron.

The poisons formed in the blood by germs in acute diseases are among the most common sources of headache. In these disorders there is always fever and often backache, and general soreness in the muscles. One of the most prominent symptoms in typhoid fever is constant headache with fever increasing toward night, and also higher each night than it was the night before. The headache and fever, together often with occasional nosebleed and general feeling of weariness, may continue for a week or two before the patient feels sick enough to go to bed. The existence of headache with fever (as shown by the thermometer) should always warn one of the necessity of consulting a physician. Headache owing to germ poisons is also one of the most distressing accompaniments of grippe , measles, and smallpox, and sometimes of pneumonia.

The headache caused by the poison of the malarial parasite in the blood is very violent, and the pain is situated usually just over the eye, and occurring often in the place of the paroxysm of the chill and fever at a regular hour daily, every other day, or every fourth day. If the headache is due to malaria, quinine will cure it. The headache of rheumatism is owing also to a special poison in the blood, and is often associated with soreness of the scalp. If there are symptoms of rheumatism elsewhere in the body, existing headache may be logically attributed to the same disease (see Rheumatism).

The poison of gout circulating in the blood is sometimes a source of intense headache.

The headache of Bright’s disease of the kidneys and of diabetes is dull and commonly associated with nausea or vomiting, swelling of the feet or ankles, pallor and shortness of breath in the former; with thirst and the passage of a large amount of urine (normal quantity is three pints in twenty four hours) in the case of diabetes.

The headaches of indigestion are also of poisonous origin, the products of imperfectly digested food being absorbed into the blood and acting as poisons.

Another variety of headache due to poisoning is seen in children crowded together in ill ventilated schoolrooms and overworked. Still another kind is due to inhalation of illuminating gas escaping from leaky fixtures.