<unk> s are insects from the genus Cimex that feed on blood, usually at night. Their bites can result in a number of health impacts including skin rashes, psychological effects, and allergic symptoms.<unk>  bites may lead to skin changes ranging from small areas of redness to prominent blisters. Symptoms may take between minutes to days to appear and itchiness is generally present. Some individuals may feel tired or have a fever. Typically, uncovered areas of the body are affected. Their bites are not known to transmit any infectious disease. Complications may rarely include areas of dead skin or vasculitis.<unk>  bites are caused primarily by two species of insects: Cimex lectularius (the common<unk>  and Cimex hemipterus, found primarily in the tropics. Their size ranges between 1 and 7 mm. They spread by crawling between nearby locations or by being carried within personal items. Infestation is rarely due to a lack of hygiene but is more common in high-density areas. Diagnosis involves both finding the<unk> s and the occurrence of compatible symptoms.<unk> s spend much of their time in dark, hidden locations like mattress seams, or cracks in a wall. Treatment is directed towards the symptoms. Eliminating<unk> s from the home is often difficult, partly because<unk> s can survive up to 70 days without feeding. Repeated treatments of a home may be required. These treatments may include heating the room to for more than 90 minutes, frequent vacuuming, washing clothing at high temperatures, and the use of various pesticides.<unk> s occur in all regions of the globe. Infestations are relatively common, following an increase since the 1990s. The exact causes of this increase are unclear; theories including increased human travel, more frequent exchange of second-hand furnishings, a greater focus on control of other pests, and increasing resistance to pesticides.<unk> s have been known human parasites for thousands of years.
Bed bug
Scabies
Pinworm 
Allergy
Hookworm
Dermatitis herpetiformis
Head louse
Deer fly