(Reuters) - Illinois children and adults with epilepsy will soon be allowed to use marijuana to ease their symptoms under a law signed on Sunday by Democratic Governor Pat Quinn, the latest in a series of measures loosening restrictions on cannabis by U.S. states.

The move to add epilepsy and other seizure disorders to the list of conditions legal to treat with marijuana or its extracts comes as numerous states have made medical use of the drug legal. Two states, Colorado and Washington, have legalized its recreational use.

“This new law will help alleviate the suffering of many adults and children across the state,” Quinn said in statement. “Epilepsy is a debilitating condition, and this much-needed relief will help to reduce some of its symptoms for those who endure seizures."

The Illinois law, which takes effect in January, would allow children who experience seizures to be treated with non-smokable forms of cannabis, as long as they have permission from a parent.

“I have a 14-year-old constituent by the name of Hugh who lives with epilepsy,” said Republican state lawmaker Jim Durkin, who co-sponsored the new law. “His parents, Bob and Kelly, want to provide their son with as much relief as possible. Unfortunately, traditional medications and methods have not worked."

The state is putting the final touches on a broader medical marijuana plan, a tightly regulated program whose regulations were finalized just last week.

Residents will be allowed to apply for permission to use the drug to treat medical conditions in September, and the full program is expected to be up and running early next year, Quinn spokeswoman Katie Hickey said on Sunday.

(Reporting by Sharon Bernstein in Sacramento; Editing by Dan Grebler)