His expertise is small and autonomic nerve fiber neuropathy. Dr. Illigens investigates the effects of small fiber injury on sudomotor, vasomotor and pilomotor responses as well as the impact on wound healing. Medical personnel and research staff are trained by him to become proficient in peripheral nerve fiber evaluation. The fellows and students are required to actively participate in research projects that Dr. Illigens designs and supervises.

He published his research in respected peer-reviewed journals and presented these studies in over 40 abstract publications and conference presentations. Additionally, Dr. Illigens is a certified applied biostatistician and lecturer in the Harvard Medical School course Principles and Practice in Clinical Research, where he mentors students to learn the theoretical background and practical application of clinical research, study design, statistical methods and data collection.