In the Netherlands, during the tax return, health costs that are not reimbursed by the insurer and do not fall under the annual deductible can be deducted. This includes, for example, dentist costs, glasses, contact lenses, and physiotherapy costs that have to be paid out of pocket.
There are also those who follow a special diet due to allergies, and a fixed amount can be deducted for these costs during the annual tax return. For example, if someone follows a lactose- and gluten-free diet, they can deduct €1050 annually for these costs. It is important that the allergy is known to the general practitioner.
This link provides information on which costs can be deducted for certain diseases.