The cost of home improvements is not normally allowed as a medical expense deduction. Instead, home improvements are added to the cost basis of your home and may reduce your capital gains when you sell. Home improvements that are medically necessary may be taken as a deduction if they are a type of improvement that does not increase the selling value of your home. The IRS gives hand rails and grab bars as an example of improvements that usually do not raise the value of the home. I could not say for this type of therapy room. If audited, you would have to prove it does not raise the selling value of the home. You might want to ask a real estate professional. You might have to split the cost (for example, if you add a sun room and then install medical equipment, the sun room might be a non-deductible improvement, assuming the equipment could be removed so a new owner could enjoy the sun room. But the medical equipment would be deductible.)
Then, you can deduct costs to cure or treat a disease or condition. There is some question over whether red light therapy actually works. I'm not qualified to determine that, so you probably need a letter of medical necessity from your doctor that specifies what condition(s) you have, how red light therapy will benefit you, and recommending a course of treatment, that fits with the equipment you installed.
