"Lathered up" is a commonly used phrase that describes the act of working up a soapy suds or foam, especially when washing or bathing. However, there are several other synonyms that could be used in place of this phrase. Some examples include 'frothy', 'bubbly', 'foamy', 'creamy', 'soapy', 'sudsy', 'fizzy', and 'effervescent'. Each of these synonyms has a unique characteristic that could be used to accentuate the context in which it is used. Therefore, whenever one wants to express the act of producing a soapy suds or foam, they can easily use any of these synonyms to add variation and interest in their prose or speech.