Color-Run on Clothing

I have a ladies store.I sold a knit twinset to a customer, and she came back after having worn it that the colour had run. I looked at it and told her where the colour had run was under her arm next to her body ,and what caused the colour to run was due to sweat, which in this case I cannot garantee a garment due to sweat-perspiring. I explained to her that the colour hadn’t run in any other place, but just under the arm. My customer wants me to refund her, but I dont think I have to, as sweat on clothes no one can garantee.

I would like an answer from a Rav
Is it possible to have an answer in English.And also Q&A IN Hebrew.

Thank you

Answer:

In such matters, the halachah depends on the common custom among stores (because the buyer can assume that the items are sold under guarantee according to the general custom), unless stated otherwise.

I understand that your store has a general guarantee, and the question is if this case is included or not. If the general custom is not to offer a guarantee for sweat-caused colour runs, then you don’t have to do anything beyond the common custom.

This answer assumes that the item in question was not flawed. If the item was actually flawed, the customer would be in her right to void the sale.

Sources: See (for instance) Maharshdam, Yoreh De’ah 101 and 221, and Choshen Mishpat 20 and 175.