Isodose 20 Gy found as a threshold dose for radiation recall dermatitis.

Area of Science:

• Dermatology
• Radiotherapy
• Pharmacology

Background:

• Radiation recall is an uncommon reaction where skin exposed to radiotherapy reacts to certain medications.
• This phenomenon typically occurs months to years after initial radiation treatment.

Observation:

• A patient developed severe radiation recall dermatitis after applying a topical natural cream 2 years post-radiotherapy.
• The reaction was confined to the irradiated skin volume, specifically matching the 20 Gy isodose line.

Findings:

• The topical cream triggered a localized skin reaction only within the previously irradiated area.
• No radiation recall reaction was observed in areas receiving lower radiation doses (5-15 Gy) despite similar cream application.

Implications:

• This case report may establish a minimum threshold dose of 20 Gy for topical cream-induced radiation recall dermatitis.
• Understanding radiation recall thresholds can inform clinical management and patient counseling regarding post-radiotherapy medication use.