However, with continued exposure and at high levels, the poison may deaden a person's sense of smell, making the individual unaware that he or she continues to be exposed to hydrogen sulfide. If the rotten egg odor is no longer noticeable, it may not necessarily mean that exposure has stopped. After a serious exposure, symptoms usually begin immediately. At low levels, hydrogen sulfide causes irritation of the eyes, nose, and throat. Moderate levels can cause headache, dizziness, nausea, and vomiting, as well as cough and breathing difficulty.
Higher levels can cause shock, convulsions, coma, and death.
The main treatment is to remove the victim from exposure and give fresh air and oxygen, and to take the person to an emergency medical facility for evaluation. There is no proven specific antidote for hydrogen sulfide poisoning. After a single, small exposure with quick recovery, no delayed or long term effects are likely to occur. After a serious exposure that causes coma or convulsions, damage may have been done to the brain and heart. Specific tests for the presence of hydrogen sulfide in blood and urine are not medically useful.