Hello ma'am,
My research has not found any product, vitamin or supplement that has demonstrated efficacy or benefits for the immune system, mental health, or concentration.
Instead, look to non-pharmacological measures:
Make sure you eat plenty of fruits and vegetables, get the right amount and quality of sleep, and manage stress well if possible, among other things.
For concentration, for your study environment, reduce distractions as much as possible, such as cell phones, computers, television and noise... write down your study or work goals on a list to evaluate your progress and to stay on track.
Take frequent short breaks (5 minutes every hour for example).
Finally, exercise and an adequate amount of sleep can greatly help you relax and assimilate the material being studied.
For the skin:
The basis of treatment is moisturizing the skin and other non-pharmacological measures:
A fragrance-free moisturizer such as Aveeno, Cutibase, Base Glaxal, Cerave and others should be applied as often as needed. The cream should be applied whenever the need to scratch arises, among others.
Avoid scented soaps, and after the bath or shower, avoid rubbing the skin vigorously: instead, lightly pat the skin to leave a thin layer of moisture, then apply the moisturizing cream within 5 minutes of getting out of the bath.
In cold weather, make sure your child wears gloves and that his or her neck and face are well protected (scarf, neck warmer)
For hair, no supplement has been shown to be beneficial unless a deficiency is detected, which can only be done with a blood test. Otherwise, it is unlikely that supplements will provide any benefit.
I hope I've been helpful and remain available if there is anything I can do
Tom Samaha, pharmacist