Fleas are small to microscopic insects that feed on the blood of humans and animals by piercing their skin. The bites usually leave small red bumps, but may also cause a rash or hives. They itch intensely, and a person or a pet may scratch them and cause larger sores that can become infected. Fleas can also spread diseases to people and animals. Malathion is commonly used to kill fleas, but it should be used with caution.

Scratching Siberian Husky
credit: Pattie Steib/Hemera/Getty Images
Dog scratching fleas on grass

Application

Treat only the outside areas where pets or other animals play or live. Remove animal droppings and other debris from the area. Mix 5 ounces of 57 percent malathion in 1 gallon of water and use a garden sprayer to apply the malathion mixture at the rate of 1 gallon per 1,000 square feet. Do not apply in windy or wet weather.

Warnings

Wear long sleeves, long pants, socks, shoes and gloves when applying malathion. Remove your clothing immediately afterwards and wash separately from other laundry. Wash your hands and any exposed skin before eating, drinking, smoking or using the toilet. Do not inhale or ingest malathion; do not get it on your skin or in your eyes. Malathion is toxic to fish and aquatic wildlife -- do not contaminate bodies of water or drinking water. Keep people and pets out of treated area for 12 hours.