Malaria is a parasitic disease caused by Plasmodium parasites, transmitted to humans through the bite of infected female Anopheles mosquitoes. This illness is commonly associated with symptoms such as fever, fatigue, vomiting, and headaches. While these systemic effects are widely recognized, malaria also presents a range of notable and diverse manifestations involving the skin.
Skin Manifestations of Malaria
Malaria directly impacts the skin through several mechanisms, reflecting the body’s response to the parasitic infection. A common sign is pallor, or paleness, which occurs due to anemia. The malaria parasite, particularly Plasmodium falciparum, infects and destroys red blood cells, leading to a significant decrease in their number and consequently, reduced oxygen-carrying capacity in the blood.
Jaundice, characterized by a yellowing of the skin and whites of the eyes, can also develop in severe malaria cases. This happens when the breakdown of red blood cells releases a substance called bilirubin, which then accumulates in the bloodstream due to liver dysfunction. Elevated bilirubin levels indicate that the disease has progressed to a more serious stage. While traditionally considered a damaging sign, some research suggests that bilirubin buildup might offer a protective role against the infection.
Small red or purple spots on the skin, known as petechiae and purpura, can arise from low platelet counts, a condition called thrombocytopenia. Platelets are blood components involved in clotting, and their reduction can lead to issues with blood coagulation and bleeding under the skin. This manifestation is more commonly observed in Plasmodium falciparum malaria, though it can occur in Plasmodium vivax cases as well.
Other skin changes, though less common, can include urticaria, also known as hives, and various nonspecific rashes. Urticaria may appear as itchy wheals and angioedema, thought to be caused by an antigen-implicated response involving IgE mediation or mast cell degranulation, which releases histamine and other inflammatory mediators. Reticulated erythema, presenting as a net-like rash, has also been reported in some malaria patients, particularly in children and adolescents. These dermatological signs are direct consequences of the disease process, rather than side effects of treatment.
The Skin’s Role in Malaria Transmission
Beyond displaying symptoms, the human skin plays a role in the malaria parasite’s life cycle, particularly in facilitating its transmission back to mosquitoes. The skin serves as a reservoir for gametocytes, which are the sexual-stage parasites that mosquitoes ingest when taking a blood meal. While gametocytes circulate in peripheral blood, studies indicate that mosquitoes can acquire infections even from individuals with low gametocyte densities that are often undetectable by standard microscopy.
Research has explored whether gametocytes might sequester or aggregate in the subdermal capillaries of the skin, increasing the likelihood of mosquito uptake. While some studies have hypothesized skin sequestration, current data strongly suggest there is no significant sequestration of P. falciparum gametocytes in the skin, meaning peripheral blood gametocyte densities are reliable for predicting transmission potential. However, mosquito infection rates are often higher when mosquitoes feed directly on the skin of gametocyte carriers compared to feeding through artificial membranes.
Malaria infection also subtly alters a person’s skin odor, making them more attractive to mosquitoes. This manipulation occurs through changes in volatile organic compounds (VOCs) emitted from the skin. For instance, infected individuals have been shown to produce greater amounts of certain aldehydes, such as heptanal, octanal, and nonanal, which are detected by mosquito antennae and increase their attraction. This alteration in human body odor is hypothesized to be an adaptive strategy by the parasite to increase vector-host contacts and facilitate its spread.
Cutaneous Reactions to Antimalarial Drugs
Antimalarial medications can lead to various skin-related side effects. Doxycycline, commonly used for malaria prophylaxis, is known to cause photosensitivity. This reaction makes the skin unusually sensitive to sunlight, leading to exaggerated sunburns, redness, pain, and sometimes blistering, even with brief exposure. It occurs because doxycycline absorbs UV radiation in the skin, generating reactive oxygen species that damage cells. Patients are advised to use broad-spectrum sunscreen and wear protective clothing to mitigate this risk.
Chloroquine and hydroxychloroquine are other antimalarial drugs that can induce cutaneous reactions. Pruritus, or itching, is a common side effect, particularly noted in individuals of African descent, with an estimated prevalence of less than 10% for hydroxychloroquine. These medications can also cause hyperpigmentation, appearing as a bluish-gray to black discoloration of the skin and oral mucosa, which may affect 10-30% of patients on long-term treatment. While often improving after discontinuation, the discoloration may not entirely resolve.
Mefloquine, another antimalarial, is associated with dermatological effects such as pruritus and maculopapular rashes, which can occur in approximately 4-10% and up to 30% of users, respectively. Other less common reactions include urticaria and facial lesions. Patients may also experience general skin rashes, flushing, or redness.
Though rare, severe and potentially life-threatening cutaneous adverse reactions can be triggered by antimalarial drugs. These include Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), which involve widespread blistering and peeling of the skin. While uncommon, SJS has been reported with drugs like Malarone (atovaquone/proguanil combination) and sulfadoxine-pyrimethamine. It is important for patients to promptly report any new or worsening rash or skin issue to their healthcare provider while undergoing antimalarial treatment.