According to the Illinois Poison Center, soap may cause irritation to the stomach or intestines if swallowed. However, hand and body soaps are minimally toxic in very small quantities, such as when someone licks or tastes a bar of soap. Nausea and intestinal upset are the most common symptoms.
The New York Times suggests that vomiting and diarrhea are the most common effects of soap ingestion. The suggested course of action following soap ingestion is to give the patient milk or water, contact a poison control hotline and monitor the person who ate the soap. If the patient goes to the emergency room, the doctors will monitor his vital signs, including pulse rate, blood pressure and temperature, and treat any issues as necessary.
Healthline cautions that commercial soaps may cause more serious health problems. Some strong detergents or soaps may cause irritation, burns or even little holes in the skin. Some soaps may even cause the throat or tongue to swell, which can inhibit the ability to breathe and swallow. Soap poisoning may lead to a dangerous drop in blood pressure or a change in the pH of a person’s blood, either of which can damage the body’s internal organs.