Toxic squash syndrome is a rare condition that causes a person to have a rash on the skin and an upset stomach. The condition is caused by eating poisonous or toxic squash. The symptoms include a yellow discoloration of the skin, toxic intestinal symptoms, and the rash. The syndrome is fatal only about 10% of the time. The symptoms of toxic squash syndrome are not fatal. The symptoms of toxic squash syndrome are not fatal, and the syndrome can be treated with a variety of non-toxic treatments. The syndrome is caused by eating poisonous or toxic squash.