Can deodorant cause lumps under the armpit? Deodorant does not cause lumps in the armpit. Antiperspirants, on the other hand, may lead to armpit lumps. MedlinePlus. Armpit lump. MedlinePlus.
The NHS says most lumps are “harmless” ― but they ... in a circular motion all the way up to your collarbone and under each armpit. Use a mix of light and firmer pressure.