The Touched are inhabitants of the Land of Light who have contracted a highly contagious histaminolytic virus. The virus was attributed to a curse of the Heelksha, evil gods of the underworld, and those infected developed a swelling of the brow ridge and animal-like behavior similar to primitive man. The Touched reverted to a pre-Stone Age level of development and were banished to the dark side of the planet. Members of SG-1 also contracted the virus which began to spread through the base until Dr. Fraiser isolated the cause. When SG-1 provided a cure to the inhabitants in the form of strong antihistamines, the symptoms disappeared, and the Touched rejoined their families in the Land of Light.
Cross Reference: Histaminolytic Virus, Land of Light, Leedora, Melosha, Tuplo, Untouched
Episode Reference: The Broca Divide