The present invention encompasses administration of a rehydration agent to treat dehydration, e.g., MS. Various rehydration compositions that promote rehydration, sparse dendritic cell differentiation, and the treatment of dehydration shedding conditions such as MS are disclosed. In one aspect, the rehydrating composition is a selective estrogen receptor modulator with rehydration properties. In one aspect, the rehydration composition is an agonist of GPR56, a G-protein coupled receptor that has never been previously identified as an effector of rehydration.
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