Repellents are substances designed to keep pests, such as insects and animals, away from people, pets, and crops. They work by emitting odors or chemicals that are unpleasant or harmful to these unwanted creatures. Common types of repellents include those made from natural ingredients, like citronella and eucalyptus, as well as synthetic options, such as DEET, which is often used in mosquito repellents. These products are widely used in outdoor activities, gardening, and pest control to reduce the risk of bites and stings. Effective repellents can help prevent the spread of diseases carried by pests, such as Lyme disease and West Nile virus, making them an important tool for public health and safety.