Kwell shampoo is a prescription-only product that eliminates head lice and scabies (mites). It contains the active ingredient lindane, an insecticide. Lindane is less effective than many other treatments, taking longer to kill the pests, according to the University of Nebraska–Lincoln (UNL) Extension. Because severe side effects are possible, people should only use lindane if they can't tolerate other medications or if other medications haven't worked, as advised by the U.S. Food and Drug Administration (FDA). The shampoo should only be used once.
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Seizures and Death
Rarely, seizures and deaths have been reported after lindane use, mainly associated with repeated or prolonged application, according to Drugs.com. Some reports of seizures and deaths involved only one application of lindane used according to directions. People with uncontrolled seizure disorders should not use Kwell shampoo. The FDA warns that lindane products should not be used on babies or children, elderly people, and people weighing less than 100 lbs. Additionally, people with skin conditions such as psoriasis or eczema shouldn't use lindane, as they're more likely to absorb the substance through skin sores. Women who are breastfeeding shouldn't use lindane because it may transfer to the baby.
Central Nervous System Effects
Using a lindane product such as Kwell shampoo can lead to other symptoms of neurotoxicity or negative central nervous system effects, although this is rare. Drugs.com and the U.S. National Institutes of Health say these side effects can include clumsiness, dizziness, drowsiness, headache, unsteadiness, irritability, nervousness, muscle cramps, rapid heartbeat, restlessness, uncontrollable shaking and vomiting.
Skin Side Effects
More commonly, Kwell shampoo causes skin irritation. Users of lindane products may develop burning and stinging sensations, dry skin, hair loss, itching, numbness, tingling, rash and skin redness, as listed by the NIH.
Some people may experience a severe allergic reaction to Kwell shampoo, although this is rare. Symptoms include a severe rash, hives, trouble breathing, tightness in the chest, and facial or mouth swelling. An allergic reaction to Kwell shampoo should be considered a medical emergency.