Mosquitoes are known to carry many infectious diseases from several different classes of micro organisms, including viruses and parasites. Mosquito born illnesses include Malaria, West Nile Virus, Elephantiasis, Dengue Fever, Yellow Fever, etc.
Mosquitoes are most effectively repelled by Deet, but wearing long pants and a long sleeve shirt can help as well. If you are bitten, a soothing lotion or but treatment may reduce the discomfort, swelling and itching.
Should you choose not to use Deet, there are several homemade recipes on the internet to choose from