For example, exposure to pyrethrum can trigger an asthma attack at a trivial dose of exposure. The answer is not simple. The active ingredient is usual-ly a single, highly purified component although it may be a combination of two or more pesticides. Usually, the inert ingredients consist of carriers such as petroleum distillates, but may contain other chemicals such as emulsifiers, conditioning agents or wetting agents. Their ability to irritate or sensitize is poorly understood.
Some people react to the strong odor and irritating effect of petroleum distillates.
The eyes, the mucous membranes of the nose and even the sensitive linings of the mouth and the back of the throat may feel scratchy. This is usually an annoying symptom which subsides within a few minutes after being removed from exposure to the irritant. Irritation occurs not on-ly with manmade volatile substances, but also with naturally occurring substances such as perfumes, flowers, or onions. A pesticide product which causes someone to develop severe, acute respiratory symptoms would be a true hypersensitivity to one of the active ingredients. This can occur with a limited number of specific pesticides, all requiring clinical confirmation.