HONG KONG (AP) — By day, the small commercial kitchen in a Hong Kong industrial building produces snacks. At night, it turns into a secret laboratory assembling a kit for pro-democracy protesters seeking to detox after repeated exposure to tear gas.

Volunteers seated around a kitchen island sort and pack multicolored pills into small resealable bags. At another table, a woman makes turmeric pills by dipping gelatin capsules into a shallow dish of the deep orange spice.

"Police have used so much tear gas and people are suffering," said the owner of the kitchen, speaking on condition of anonymit...