What's the plural form of Nauheim treatment? Here's the word you're looking for.
Answer
The noun Nauheim treatment can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be Nauheim treatment.
However, in more specific contexts, the plural form can also be Nauheim treatments e.g. in reference to various types of Nauheim treatments
or a collection of Nauheim treatments.