From the Guidelines

Sexual activity can have both positive and negative effects on the skin.

Sexual activity can increase blood flow and reduce stress, which can have a positive impact on the skin [no direct evidence provided].

Seminal plasma hypersensitivity can cause anaphylaxis, characterized by symptoms such as diffuse pruritus, urticaria, and pelvic pain, in rare cases 1.
Vaginal dryness and dyspareunia can occur due to various factors, including chemotherapy, radiation therapy, and treatment with aromatase inhibitors 1.
Chronic genital disorders, such as lichen sclerosus, can lead to psychosexual problems and sexual dysfunction 1.
Skin fibrosis and loss of sexual sensitivity can occur due to radiation therapy 1. It is essential to note that these negative effects can be managed with proper treatment and care, such as the use of nonhormonal, water-based lubricants and moisturizers, and referral to a specialist for psychosexual support 1.

From the Research

Sexual activity can trigger allergic reactions, such as contact dermatitis, due to latex in condoms, substances in lubricants, spermicides, topical medications, and cosmetics 2.
Seminal fluid proteins can cause hypersensitivity reactions, known as seminal plasma hypersensitivity 2.
Sexual activity itself can trigger symptoms in patients with respiratory allergies, such as honeymoon asthma and rhinitis 2.

Chronic skin diseases, such as vitiligo and chronic urticaria, can have negative impacts on sexual life, including lower sexual drive, difficulties in sexual arousal, and reduced satisfaction from orgasm 3.
Acne, psoriasis, and atopic eczema can affect sexual functioning and relationships, with effects on self-perceived sexual attractiveness, self-confidence, and capacity for intimacy 4.
Atopic dermatitis can cause physical discomfort, changes in physical appearance, and low self-confidence, interfering with sexual well-being and partnered relationships 5.

Sex hormones, such as oestrogens, progestogens, and androgens, play a crucial role in skin metabolism and can affect skin elements, including collagen production, sebaceous glands, and hair growth 6.
Hyperandrogenism and disturbances of reproductive functions can lead to skin manifestations, such as acne, hirsutism, and androgenetic alopecia, due to abnormalities in GnRH pulsatility, hyperoestronaemia, and adrenal hyperandrogenism 6.