What is the difference between Lysine and L-Lysine 1000 MG or 500 Mg in the use for cold sores There are 4 question to answer here My 12 year old Boy has cold sores but the Doctor, she would not give him a blood test to find out if it is Herpes simplex 1 or 2 and the doctor said, they were contagious The Doctor said if he took L-Lyine every day for the rest of his life he would not ever have another brake out again, but she did not know what strength he should take, at Walmart they have 1000 MG and 500 MG he only weights 83 pounds, But I am afraid of long term Medicines. What are the side affects Of L-Lyine taken every day for the rest of your life? and what strength should he take?or is there another prescription drug that is more effective? or is there a cure? I am afraid of Medicines they damage your Liver and Kidneys. What does L-Lyine do to a 80 pound Boy after taking it long term ?