In biology, poisons are substances that cause disturbances in organisms, usually by chemical reaction or other activity on the molecular scale, when an organism absorbs a sufficient quantity. The fields of medicine (particularly veterinary) and zoology often distinguish a poison from a toxin, and from a venom. Toxins are poisons produced by organisms in nature, and venoms are toxins injected by a bite or sting (this is exclusive to animals).
A problem with your jaw. Earache is occasionally caused by a problem with the joint of your jaw bone (where the jaw meets the skull). This is known as temporomandibular joint pain and can be caused by problems such as arthritis or teeth grinding.
How can this pain in or near the ear be caused by stress? Frequent clenching of the jaw is a habit of many people. Often this is a stress related problem that causes the person to bite on pens, pencils, or fingernails. This often happens during sleep also with grinding of the teeth, and clenching of the jaw.