A frequently used, commercialised product is 'hot oil treatment pack for hair', to 'add life and vitality' (as the blurb says) to your hair.
At first I thought 'mascarilla' was for the face, as that is more it's literal meaning, to 'mask' the face, e.g. , but I see it's for the hair, so you can't call it a mask. Yet to call it an 'oil' unless it's really an oil, would be inappropriate.
I suggest the following, depending on the sententence/context:
oat treatment pack for the hair
oat hair treatment (product)
Pack is OK here, becuase we also say 'face pack' to refer to 'mascarilla' for the face.
Hope this is of some help.
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Native speaker of: English
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