Conditions treated

Guides to the skin conditions Dr. Nathan diagnoses and treats most often: signs, tests and treatment options.

Written by Dr. Neera Nathan, MD, MSHS, board-certified dermatologist Last updated Sources cited Editorial policy

How a skin concern is usually worked out

Most diagnoses come from putting a few pieces together, in roughly this order.

  1. Your storyWhat changed, when, and what you've tried
  2. A careful lookSkin, scalp, nails and the areas that are easy to miss
  3. A diagnosisSometimes from the exam, sometimes after a biopsy
  4. A planOptions with their benefits and risks, in plain language
  5. Follow-upCheck progress and adjust until it works for you

Condition guides

Select a condition to open it.

Skin cancer and precancers

The most common skin cancer, with about 3.6 million cases diagnosed in the U.S. each year. It grows slowly and rarely spreads, but it can damage nearby tissue if left alone.1

Signs

  • A pearly or translucent bump
  • A pink patch or a sore that bleeds, crusts and doesn't heal
  • A scar-like area with no injury to explain it

Diagnosis

  • Skin exam with a dermatoscope
  • Biopsy to confirm the type
  • Risk features: size, location, subtype and whether it has come back

Treatment

  • Surgical excision for many low-risk tumors
  • Mohs surgery for higher-risk tumors or sensitive areas
  • Other options in selected cases, such as scraping and burning, creams or radiation

Guideline basis23

The second most common skin cancer, often on sun-exposed skin. Most begin as actinic keratoses, and high-risk tumors need prompt, complete treatment.4

Signs

  • A firm red bump, or a scaly patch that thickens
  • A sore that keeps opening
  • A growth that is tender or grows quickly

Diagnosis

  • Biopsy
  • Risk assessment: size, depth, location, nerve involvement and the person's immune status

Treatment

  • Surgical excision or Mohs surgery
  • Closer follow-up for high-risk tumors and for people with weakened immune systems

Guideline basis53

A less common but more dangerous skin cancer that starts in pigment cells. When it's found early, the five-year survival rate is 99%.1

Signs

  • The ABCDEs: asymmetry, irregular border, several colors, a diameter of about 6 mm or more, and evolving (changing)
  • An "ugly duckling": a mole that looks different from the others
  • A dark line in a nail, or a changing spot on a palm or sole

Diagnosis

  • Full skin exam and dermatoscopy
  • Biopsy of the whole lesion when possible
  • Staging based on the biopsy, which guides next steps

Treatment

  • Wide local excision with margins based on tumor thickness
  • Referral to a multidisciplinary team for more advanced disease
  • Regular skin checks afterward

Guideline basis678

A rough, scaly precancer caused by years of UV exposure. Only about 5–10% become skin cancer, but most squamous cell carcinomas start as one.4

Signs

  • Small dry, scaly or crusty patches, often easier to feel than see
  • Red, tan, pink or skin-colored
  • Common on the face, scalp, ears, forearms and backs of the hands

Diagnosis

  • Usually diagnosed on exam
  • Biopsy if a spot is thick, tender or growing

Treatment

  • Freezing for a few spots
  • Prescription creams or photodynamic therapy for larger areas
  • Daily sun protection to prevent new ones

Guideline basis4

Medical dermatology

Acne isn't only a teenage problem, and it isn't caused by poor hygiene. Effective treatments exist at every level of severity.9

Signs

  • Blackheads and whiteheads
  • Red bumps and pus-filled spots
  • Deep, painful nodules that can scar
  • Dark marks after spots heal, more noticeable on brown and Black skin

Diagnosis

  • Diagnosed on exam
  • Questions about hormones, medicines and products when acne starts in adulthood

Treatment

  • Benzoyl peroxide, topical retinoids and topical antibiotics
  • Oral doxycycline, with antibiotic courses kept limited
  • Spironolactone or combined oral contraceptives for some women
  • Isotretinoin for severe or scarring acne, or acne that hasn't responded to other treatment

Guideline basis910

A long-term, itchy inflammatory skin condition that comes and goes. The skin barrier is weaker, so daily care matters as much as medicine.11

Signs

  • Intense itch, often worse at night
  • Dry, rough or thickened patches
  • On darker skin, patches may look brown, purple or gray rather than red

Diagnosis

  • Diagnosed on history and exam
  • Patch testing if an allergic contact rash might be adding to it

Treatment

  • Moisturizers every day
  • Topical steroids, calcineurin inhibitors, PDE-4 and JAK inhibitor creams
  • Phototherapy, biologic injections or JAK-inhibitor pills for moderate to severe disease

Guideline basis121314

A chronic immune-mediated disease that speeds up skin-cell growth. It is linked to psoriatic arthritis and to heart and metabolic health, so care looks beyond the skin.15

Signs

  • Raised, scaly plaques, often on the elbows, knees, scalp and lower back
  • Nail pitting or lifting
  • Joint pain, swelling or morning stiffness, which should be mentioned at your visit

Diagnosis

  • Diagnosed on exam, sometimes with a biopsy
  • Severity based on body area and impact on daily life
  • Screening questions for psoriatic arthritis

Treatment

  • Topical steroids, vitamin D analogues and other creams for limited disease
  • Phototherapy
  • Oral medicines or biologic injections for moderate to severe disease

Guideline basis161715

A long-term condition that causes facial redness, flushing and acne-like bumps. It may be underdiagnosed in darker skin, where redness is harder to see.18

Signs

  • Flushing that becomes persistent redness
  • Visible blood vessels on the cheeks and nose
  • Bumps and pustules
  • Gritty, irritated eyes

Diagnosis

  • Diagnosed on exam
  • Eye symptoms need prompt attention

Treatment

  • Identifying triggers such as sun exposure and stress
  • Prescription creams or oral medicines
  • Vascular laser for persistent redness and visible vessels

Guideline basis18

An autoimmune condition in which the immune system attacks hair follicles, causing patchy hair loss on the scalp, brows, lashes, beard or body.19

Signs

  • Smooth, round patches of hair loss
  • Sudden loss of brow or lash hair
  • Pitting or ridging of the nails in some people

Diagnosis

  • Diagnosed on exam
  • Blood tests in some cases, to check for related conditions

Treatment

  • Corticosteroid injections or creams for limited patches
  • Oral JAK inhibitors for severe disease. Baricitinib became the first FDA-approved systemic treatment in 2022
  • Support for the emotional side of hair loss

Guideline basis1920

This information is general and doesn't replace an individual examination.

When to book a dermatology visit

  • A spot that is new, growing or changing in shape or color
  • A sore that bleeds or hasn't healed after a few weeks
  • A dark line in a nail, or a changing spot on a palm or sole
  • Acne that scars or leaves dark marks
  • Itch or a rash that disturbs your sleep
  • Scaly plaques with joint pain or stiffness
  • Sudden or patchy hair loss

Get urgent care for

  • A rapidly spreading, painful rash with fever, blistering or peeling skin, especially after starting a new medicine.
  • Vision changes or skin turning white, gray or blue after a filler injection. Call 911 if severe.
  • Swelling of the lips, tongue or throat, or trouble breathing. Call 911.

Sources

  1. The Skin Cancer Foundation. Skin Cancer Facts & Statistics. Updated March 2026. View source
  2. Work Group; Invited Reviewers; Kim JYS, Kozlow JH, Mittal B, et al. Guidelines of care for the management of basal cell carcinoma. J Am Acad Dermatol. 2018;78(3):540-559. doi:10.1016/j.jaad.2017.10.006 View source
  3. Connolly SM, Baker DR, Coldiron BM, et al. AAD/ACMS/ASDSA/ASMS 2012 appropriate use criteria for Mohs micrographic surgery. J Am Acad Dermatol. 2012;67(4):531-550. doi:10.1016/j.jaad.2012.06.009 View source
  4. The Skin Cancer Foundation. Actinic Keratosis. View source
  5. Work Group; Invited Reviewers; Alam M, Armstrong A, Baum C, et al. Guidelines of care for the management of cutaneous squamous cell carcinoma. J Am Acad Dermatol. 2018;78(3):560-578. doi:10.1016/j.jaad.2017.10.007 View source
  6. Swetter SM, Tsao H, Bichakjian CK, et al. Guidelines of care for the management of primary cutaneous melanoma. J Am Acad Dermatol. 2019;80(1):208-250. doi:10.1016/j.jaad.2018.08.055 View source
  7. The Skin Cancer Foundation. Melanoma Warning Signs and Images (the ABCDEs and the "ugly duckling" sign). View source
  8. American Academy of Dermatology. Finding skin cancer in darker skin tones. View source
  9. Reynolds RV, Yeung H, Cheng CE, et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol. 2024;90(5):1006.e1-1006.e30. doi:10.1016/j.jaad.2023.12.017 View source
  10. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Acne. View source
  11. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Atopic Dermatitis. View source
  12. Sidbury R, Alikhan A, Bercovitch L, et al. Guidelines of care for the management of atopic dermatitis in adults with topical therapies. J Am Acad Dermatol. 2023;89(1):e1-e20. doi:10.1016/j.jaad.2022.12.029 View source
  13. Davis DMR, Drucker AM, Alikhan A, et al. Guidelines of care for the management of atopic dermatitis in adults with phototherapy and systemic therapies. J Am Acad Dermatol. 2024;90(2):e43-e56. doi:10.1016/j.jaad.2023.08.102 View source
  14. Davis DMR, Frazer-Green L, Alikhan A, et al. Focused update: Guidelines of care for the management of atopic dermatitis in adults. J Am Acad Dermatol. 2025. doi:10.1016/j.jaad.2025.05.1386 View source
  15. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Psoriasis. View source
  16. Elmets CA, Korman NJ, Prater EF, et al. Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with topical therapy and alternative medicine modalities for psoriasis severity measures. J Am Acad Dermatol. 2021;84(2):432-470. doi:10.1016/j.jaad.2020.07.087 View source
  17. Menter A, Strober BE, Kaplan DH, et al. Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with biologics. J Am Acad Dermatol. 2019;80(4):1029-1072. doi:10.1016/j.jaad.2018.11.057 View source
  18. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Rosacea. View source
  19. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Alopecia Areata. View source
  20. U.S. Food and Drug Administration. FDA Approves First Systemic Treatment for Alopecia Areata (news release, June 13, 2022). View source

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