What Causes Keloid Formation At Surgery Scar Site?

Sir, I had a tummy tuck surgery 3 months back. The surgery scars have healed but now I have keloid on these scars. I am a non-vegetarian and takes drinks (liquor) daily. I have had surgeries before but then I had no keloid. This is the first time. Is alcohol a reason for occurance of keloid now ? I am 37 years old, female, 162, weigh 84 kg from Kerala, India. I am taking thyronorm 50 mg for the last 3 years.