Exposure to solar radiation (which includes ultraviolet, visible, and infrared light) and excess heat can have a profound and cumulative impact on skin health. These five effects cover both immediate reactions and long-term damage:

Photoaging (Wrinkles and Laxity)

Cause: Primarily UV light (UVA and UVB) and Infrared (IR) radiation (heat).

Effect: The radiation penetrates the skin and generates free radicals and enzymes (like MMPs) that degrade and break down collagen and elastin fibers. This leads to the characteristic signs of sun damage: premature wrinkles, fine lines, rough texture, and loss of skin firmness (laxity). IR radiation, or heat, is increasingly recognized as a contributor to this process.

Hyperpigmentation (Dark Spots and Uneven Tone)

Cause: UV light (especially UVA), Visible Light (like blue light), and Heat.

Effect: Light and heat stimulate melanocytes—the cells that produce skin pigment (melanin). This results in uneven skin tone, sun spots (lentigines), and the worsening of conditions like melasma. Visible light, in particular, is a major trigger for hyperpigmentation in darker skin tones.

DNA Damage and Carcinogenesis (Skin Cancer)

Cause: Primarily UVB and UVA light.

Effect: UVB radiation is the most potent cause of DNA damage, leading to genetic mutations within skin cells. This damage can suppress the immune system and, over time, lead to the formation of precancerous lesions and various types of skin cancer, including basal cell carcinoma, squamous cell carcinoma, and melanoma.

Inflammation and Erythema (Sunburn and Redness)

Cause: UV light (acute, intense exposure) and Heat (thermal burns or chronic exposure).

Effect: Sunburn is an acute inflammatory reaction to UV overexposure, causing skin cell death, redness (erythema), and pain. Heat alone can cause burns, or, through chronic low-level exposure, can lead to a condition called Erythema Ab Igne (“toasted skin syndrome”), which is a hyperpigmented, net-like rash caused by damage to blood vessels and elastic fibers.

Compromised Barrier and Hydration

Cause: Heat and increased sweating.

Effect: High temperatures and excessive sweating cause the skin to lose moisture rapidly, leading to dehydration, dryness, and a compromised skin barrier function. Furthermore, the combination of sweat, oil, and heat can clog pores, leading to acne flare-ups or heat rashes (miliaria).