Parasitic infections are susceptible to cause a wide range of non-specific symptoms. Skin manifestations, such as rashes, are one of them. However, these symptoms include a lot of different skin manifestations and are not specific to parasitic diseases, as a wide range of conditions can cause them. As such, skin rashes may be associated with parasitic diseases, but are not a well-known frequent and recognisable symptom of this type of infections.
Itchy skin rashes and dermatitis can occur as early infection symptoms of some parasitic diseases. In fact, these symptoms are frequently associated to manifestations at the site of the penetration of the larvae within the skin. As such, parasites known to penetrate the host’s skin in their larval form in order to establish an infection, including some roundworms also known as nematodes as well as the flatworm Schistosoma, are known to cause skin manifestation, at least in the early stage of the infection. However, these parasites are usually not found in developed countries.
Furthermore, few parasitic diseases, such as the cutaneous form of the infection with the protozoan parasite Leishmania, can cause a kind of skin disease. The clinical manifestation of this parasite is characterised by the apparition of an ulcerative lesion at the site of parasite’s inoculation by the sandfly.
Human can also be affected by a condition called cutaneous larva migrans. This disease is caused by the accidental infection of human by some animal’s hookworms. Larvae that penetrate the human skin cause red and intensely itchy skin rashes. The skin manifestation follows the day-to-day movement of the larvae within the human body, as implied by the name of the disease. This affection usually resolves by itself within 5 to 6 weeks because of the death of the larvae that is not able to establish a real long-lasting infection within human. However, the severity of the symptoms, especially the itching part, usually leads the infected person to request a medical consultation and to be treated by an anti-parasitic drug that cures the disease.
Rather than being simply a symptom, skin rashes also occur in certain people as an allergic manifestation due to the parasites colonising the gastrointestinal tract. In that case, the parasite triggers an immune response in the human host already predisposed to allergic manifestations. Treatment of the parasitic infection is usually sufficient to cure the concomitant allergy.
Another allergic skin reaction caused by parasites is commonly known as the swimmer’s itch and is present worldwide. This disease us characterised by red itchy papules appearing usually on the skin in the hours after swimming outdoors in untreated contaminated waters, such as lakes or rivers. Swimmer’s itch is caused by parasites from the same family than the human-infecting Schistosoma. However, these specific parasites are not able to successfully infect humans, but rather infect other vertebrates. Larvae are present in untreated waters because freshwater snails are the intermediate host releasing them. When someone swims in contaminated water, the larvae penetrate the skin. However, as they cannot fulfill their life cycle in human, they die quickly. The observed skin rash is in fact an allergic manifestation to the presence of the larvae within the skin. As they subsequently die because they are not able to establish an infection in human, the rash will usually resolve by itself within a week. Nevertheless, it is important to limit the scratching of the skin in the infected areas in order to prevent getting a secondary bacterial infection.
Finally, as skin rashes are not a frequent parasitic diseases’ manifestation, you should probably look for other causes when experiencing it, except for the common swimmer’s itch.