De-toxing is a fairly common response to massage, especially if you have not been getting bodywork done on a regular basis. Massage releases toxins held in your system, so as the toxins move and purge you may experience feeling very mild nausea, achiness, or a headache. This should pass within a couple of hours. Be sure to drink water to assist in release and take a nap if possible. You should feel lighter, clearer, and more refreshed after the de-tox has passed.