Red bumps from bathing in the river may be due to an allergic reaction caused by contact with certain substances in the river water, possibly hives. First of all, you should avoid bathing in the river, which can be treated with topical ointment and oral antihistamine medication. 1. Avoid contact with allergens: there are more substances in the river, so avoid bathing in the river again and contacting allergens that cause allergic reactions. 2. Topical ointment: The red bumps may be wind-breaks, which can be treated with topical glycerine lotion or benadryl cream to stop the itching. 3. Oral medication: antihistamine medication such as loratadine and cetirizine can be taken orally. In severe cases, oral glucocorticoids can be taken. River bathing red bumps may also be allergic contact dermatitis and other causes, it is recommended to go to the hospital in a timely manner, to clarify the cause of the disease, give targeted treatment or treatment.