What Causes Roughness With Darkening Of Skin?

my son (14 yrs )is having chronic skin problm.started since he was 1yr old.itching also there.when the climate changes it increases more.he was suffering from wheezing allerging problems like running nose sneezing but it got reduced with ayurvedic treatment.but skin is very rough and dark in color.he turned to vegetarian now.he's taking ayuvedic medicines now.before he used to take inhalation antibiotic frequently but nw no medicines.pls advise as we dont know what to do now.He's in grade 10.healthy.good in studies