30ml is equal to 1.01 ounces or 3/4 of a shot glass. Uh does this only
occur when drinking Scotch Whiskey or when drinking all kinds of Whiskey?
Sounds to me like a sensitivity to whiskey alcohols all together.I could see
your reaction to Scotch if it was like 6 or 8 ounces of Liquor but one shot
glass is something else. Personal suggestion is find something other than scotch to drink , or better yet don't drink alcohol at all.
Does it matter what brand of Scotch you drink? It could be the additives in the liquor that is causing this.
You may be allergic to an additive in the drink.