Here's a challenge .....

[LennyBalls]

I am putting this on general health as it has become a health problem for the person involved.

How does one put weight on if lactose intolerant, has a nut allergy and is on ADHD that massively reduces appetite.

Tried protein shakes and goes right through and out the other end (sorry TMI). Same with complan.

Can't have cheese, butter, milk, nuts.

Any nutritionalists can help.

Not a nutritionist but (in order of healthiness and only you know what the balance is vs being very underweight / undernourished:

Avocados - energy dense, healthy fats
Hummus / beetroot dips with basic tortilla chips as snacks
Olives / tapenade
Dried fruit - easy to snack, high sugar so high calories
Olive oil / coconut oil - just add loads to stir fries / roasted veg / curries
Dark / dairy free chocolate
Dairy free cake - lots are made with oil instead of butter, I do a gorgeous dairy free carrot cake!
Deep fried anything

Sorry meant to also add to the list, the person is a very very fussy eater and wouldn't eat avocado, hummus etc.