Messi, 26, was sick on the pitch during Argentina's midweek friendly against Romania, and has been reported to have thrown up in other matches for his country and Barcelona previously.
"I've spoken with him and it happens regularly. I'm not a specialist but I understand it's not something normal," Martino said ahead of this weekend's Primera Division trip to Real Valladolid.
"He's even been to see specialists at certain times and a solution hasn't been found yet, but there's no cause for concern It doesn't affect him doing his work at all. It's something he's had for some time."
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