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Tissue Reactions: Skin, Lens, Gonads and Blood
Tissue reactions have thresholds: about 2 Gy reddens skin, 0.5 Gy can cause cataracts, and over 15 Gy to one skin field is a sentinel event.
Skin
Tissue reactions, also called deterministic effects, appear only above a threshold dose, and their severity rises with dose. Skin shows them in a predictable order. About 2 Gy causes transient erythema, a mild reddening within hours. About 3 Gy causes temporary epilation (hair loss) at about 3 weeks. About 6 Gy causes main erythema at about 10 days to 2 weeks. About 7 Gy can cause permanent epilation. Dry desquamation, or peeling, appears near 14 Gy, and moist desquamation, a weeping open surface, near 18 Gy, both about 4 weeks out. Higher doses lead to ulceration and dermal necrosis months later. The dividing basal cells of the epidermis are the sensitive layer.