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Stephen K. Tyring, M.D., PhD.

Medical Director & Board-Certified Dermatologist


A board-certified and fellowship-trained dermatologist at Dermatological Association of Texas (DAT)/ Houston Skin Associates with locations in Houston, Webster, and Pearland Texas. Dr. Tyring specializes in diagnosing, treating, and researching mucocutaneous diseases and provides exceptional personalized care to dermatology patients of all ages and backgrounds. Growing up in Indiana, he received his undergraduate degree from Indiana State University (ISU) in Terre Haute. He then earned his Master’s Degree in microbiology from Abilene Christian University (ACU) in Abilene, Texas.

After receiving his PhD in viral immunology from Texas Tech University (TTU) in Lubbock, he earned his MD from The University of Texas Medical Branch (UTMB). Dr. Tyring completed his internship in Internal Medicine at UTMB followed by a residency in Dermatology at The University of Alabama School of Medicine (UAB) in Birmingham.

He returned to Texas and joined the Dermatology and Microbiology/ Immunology faculty at UTMB, where he remained a Professor until 2004. During this time he earned an MBA from Rice University, in Houston, Texas. He then established Dermatology Associates of Texas (DAT) and the Center for Clinical Studies in Houston.


Currently, Dr. Tyring is a Clinical Professor at the McGovern School of Medicine at The University of Texas Health Sciences Center (UTHealth) in Houston. He is an active member of the American Academy of Dermatology (AAD), the Infectious Disease Society of America (IDSA), and the American Federation for Clinical Research (AFMR). Dr. Tyring has also served as the President of the Houston Dermatological Society and the Texas Dermatological Society. He sits on several editorial boards and serves as a reviewer for prestigious medical journals such as the New England Journal of Medicine, Lancet, Journal of Infectious Diseases, Journal of the American Medical Association, and Annals of Internal Medicine as well as most American and European Dermatology journals.


Dr. Tyring has been a principal investigator in over 400 clinical trials and has authored over 1000 journal articles and book chapters. In addition, he has written 11 books on dermatology, immunology, and infectious diseases.

In his current position, Dr. Tyring diagnoses and treats a wide variety of skin diseases and conducts clinical trials and basic scientific studies on diseases with infectious or immunologic etiologies. Furthermore, he teaches medical students, residents, and clinical research fellows.

Katy Hogan-Rais, PA-C

Physician Assistant


A skilled physician assistant (PA) at Dermatological Association of Texas (DAT)/ Houston Skin Associates, she specializes in dermatology and has worked as a PA since 2008 in both Internal Medicine and Dermatology.


Katy received her bachelor’s degree in biomedical science from Texas A&M University (TAMU) in College Station, Texas, and her master’s degree from the University of North Texas Health Science Center (UNT) in Fort Worth. She’s certified by the National Commission on Certification of Physician Assistants (NCCPA) and is licensed by the State of Texas Physician Assistant Board. 


In 2019, Katy earned the highest honor for dermatology physician assistants, a Diplomate Fellow of the Society of Dermatology Physician Assistants (SDPA). She’s also an active member of SDPA, where she serves on the CME Conference Committee.


Katy has expertise in performing in-office dermatological procedures. She’s also certified and trained in laser applications and cosmetic injections such as Botox, Dysport, Kybella, and dermal fillers.  She is an active member of the American Society for Laser Medicine and Surgery (ASLMS).


She maintains her medical credentials with continuing education to stay up-to-date with the latest advances in cutting-edge aesthetic and dermatological services. Katy prides herself on providing superior care for her patients and exceeding their expectations in a welcoming, comfortable setting. In her free time, Katy enjoys fitness, cooking, eating, and traveling with her husband and two children.

Alex España, PA-C

Physician Assistant


Alex was raised in New York City and received his bachelor’s degree in Ecology & Evolutionary Biology from Rice University and his master’s degree from the University of Texas Medical Branch in Galveston.


He is certified by the National Commission on Certification of Physician Assistants (NCCPA) and is licensed by the State of Texas Physician Assistant Board. He is also a member of the Society of Dermatology PAs.  Out of the office, Alex enjoys fitness, movies, arts, and culture.

Martina Goudeau, RMA, LMA

Licensed Medical Aesthetician


Martina is a Licensed Medical Aesthetician, Licensed Professional Laser Hair Removal Technician and a Registered Medical Assistant who has specialized in Dermatology and Aesthetic Skin Care for over 15 years. Working alongside some of Houston's most prominent dermatologists, Martina's love for skin care has contributed to high patient satisfaction. Utilizing her knowledge and expertise, she is passionate about helping patients achieve their skincare goals. Martina's deep understanding of various skin care products such as SkinCeutical's, Isdin, and Skin Better allow her to customize skin care routines that meet patient's unique needs.

Martina is an Esthiology graduate of the prestigious Aveda Institute. She attended the Texas Laser Institute where she obtained her certification in laser hair removal, Microneedling, and Microdermabrasion. Along with other professional training, she attended Coolsculpting University where she received her certification in nonsurgical fat reduction. She is highly skilled with extensive knowledge and training in nonsurgical facial & body contouring procedures including Ultherapy, Coolsculpting, EON and Thermage. Some of Martina's dermatology expertise include Photo Dynamic Therapy and Xtrac Excimer Laser. When Martina is not working on skin, she enjoys traveling with her husband, and spending time with her Mother and dog Carmelo.

Lina Fiorentino, LMA

Licensed Medical Aesthetician


Lina is a licensed Medical Aesthetician and a licensed Laser Hair Removal Technician. She graduated from Ogle School of Cosmetology and Esthetics and The Texas Laser Institute, where she also obtained certifications as a micro needling, microdermabrasion, non-invasive body contouring and skin tightening specialist.


Lina has more than 5 years of experience and extensive knowledge in the aesthetics industry. She is consistently working to expand her education and training in advanced skin care techniques, products, and procedures. She takes time and consideration to help and educate patients to achieve their aesthetic goals.  When Lina is not working, she enjoys spending time with her son and taking part in outdoor activities.

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