DMSA, while effective for lead and to some extent for certain other HMs, has a reputation for being tough on the immune system. I know to avoid chelation when I am fighting a cold.
I learned the hard way. On two occasions when I thought I was almost fully recovered from a sinus infection I started a new round of chelation. Within a day the infection came back.
Overall DMSA + ALA has worked for me over my 3 yrs. I've kept doses of DMSA below 25mg.
Remember in Cutler's Hg detox protocol ALA is the primary chelator. DMSA or DMPS can be useful. DMPS has a better reputation in those with immune system problems.