In their study in this issue of the JCI, Tomura et al. used mice expressing the photoconvertible Kaede protein to directly track Treg migration between the skin and LNs in the steady state (A) and during DNFB-induced allergic contact dermatitis (B and C) (17). (A) Upon photoconversion from green to red of skin-resident cells, Kaede-red CD4⁺Foxp3⁺Tregs and Kaede-red CD11c⁺ DCs became detectable in draining LNs, representing steady-state homing of Tregs and DCs from the skin to LNs. They presumably migrate through afferent lymphatic vessels. (B) DNFB-induced allergic contact dermatitis lesions contained increased numbers of Foxp3⁺ Tregs. An even more striking increase was observed in the numbers of Kaede-red Foxp3⁺ Tregs in the draining LNs, demonstrating accelerated Treg homing from inflamed skin. (C) Upon photoconversion of LN-resident cells, Kaede-red Foxp3⁺ Tregs became detectable in the DNFB-induced allergic contact dermatitis lesions. They presumably achieve this reverse migration by moving through efferent LVs, the thoracic duct, and blood vessels.