Now you can find various repellents that you apply to your skin, or other tops that prevent insects and other parasites from climbing on that surface. Indeed, these repellents are available on the basis of sound production, in particular that of ultrasound. It is true that these repellents help prevent the outbreak of insect-borne diseases like dengue fever, malaria, West Nile fever and bubonic plague. According to numerous studies and research, synthetic insect repellents tend to be more effective and longer lasting than natural repellents. While there are DEET products that can also be very effective, synthetic repellents can also provide adequate relief. Check the Internet for more information on insecticides with