Chemotherapy can heighten and alter your sense of smell.
Fragrances you once liked may become very unpleasant. This issue isn't a problem for everyone, but be aware of the possibility.
Using unscented products can help. Laundry detergent, fabric softener as well as moisturizers and cleansers can be heavily scented.
A heavily scented shampoo may leave an odor. This is especially true on wigs that have a fabric lining such as a hand tied piece or a monofilament base. Sometimes you may not notice anything after 1 or 2 washings, but the odor can build-up after several cleanings and become quite unpleasant with your heightened sense of smell.
Most of the women who have brought this to my attention were using products with synthetic fragrances, which are made of chemicals and can be nauseating. Some natural fragrences can also be quite strong and very annoying.
Using gentle, unscented products should help avoid unpleasant odors. Nausea can be a problem during chemotherapy treatment anyway, so it's best not to add anything that could trigger it or make it worse.
Hope this helps, John