NORTH Melbourne defender Scott McMahon has been hospitalised for the second time in a week as he struggles to overcome a painful viral condition that causes extreme rashes and painful joint swelling.

North director of medical services Steve Saunders told AFL.com.au on Friday that McMahon had been diagnosed with urticaria, commonly known as hives.

But Saunders said McMahon was now "tracking well" after receiving a course of cortico steroids - unlike anabolic steroids, these are not banned performance-enhancing drugs - to reduce his joint inflammation.

McMahon, who played the opening four games of the season, spent three days in hospital late last week after developing severe rashes and swelling in his hands, wrists, shoulders, elbows, knees and wrists.

Saunders said McMahon was released from hospital after an initial course of cortico steroids had brought a significant improvement in his condition. He was then prescribed a dose of oral steroids, but as his dosage was lowered his joint aches and swelling returned.

Given McMahon's relapse, Saunders said his steroid dosage would be reduced more gradually this time to ensure the urticaria does not return.

As for when McMahon can return to the field, Saunders was cautiously optimistic.

"Scotty's recovery is really something that we'll have to look at on a week-to-week basis," Saunders said.

"At this stage, you would think he'd be right to go in the next few weeks. But we've got to guard against another relapse, so we certainly won't be rushing him.

"But Scott is in the best possible hands with Dr Andy McMahon and his specialist Dr Chin, so we're confident he won't be sidelined too long."

McMahon, 25, has played 93 games for the Kangaroos since being selected at No.38 in the 2005 NAB AFL Rookie Draft.

The views in this story are those of the author and not necessarily those of the clubs or the AFL