Thank you for your query,
This itching and the red rash are looking like allergic in nature. The cause of allergy
should be looked to avoid the exposure to it.
Check for his diet, bed,pillows and clothes to look any thing is there causing allergy.
containing lotions over legs for soothing effect and you can give oral antihitamines like cetirizine
to decrease itching and allergic reactions.
Hope i have answered your query.