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