Hi, thanks for your posting your query to us.
You had a acid burn 7 years ago. By this time Scars
must be present.
Mederma cream is indicated for scars. It softens and smoothens the scars and makes them less noticeable. But this is a very slow process and at times minimal changes are noticeable even if used for a long time especially in long standing scars as in your case..This may lead to frustration. It does not give as promising results as a plastic surgery
You may use mederma on your scars but I feel you should go for plastic surgery as it will give immediate results and boost your self confidence.
But if the cost matters, you may choose between the two.
Hope this helps you.