Blood Tests for Acne, Eczema and Psoriasis

Why Skin Conditions Have Blood Test Signatures

The skin is the largest organ in the body and a visible window into internal physiology. Inflammation, hormonal excess, nutritional deficiency, and metabolic dysfunction all manifest on the skin surface — but originate in the blood. Blood tests can identify these root causes, distinguish between subtypes of the same condition, and predict which patients will respond to specific treatments.

For example, two women with clinical acne may have completely different underlying causes — one driven by insulin resistance and elevated IGF-1, the other by elevated androgens from PCOS. A blood panel distinguishes these phenotypes and changes treatment from topical creams to hormonal or metabolic intervention. Similarly, a patient with atopic dermatitis and markedly elevated total IgE may be a candidate for biologic treatment targeting IgE-mediated inflammation.

Blood Tests by Skin Condition

Condition	Key Blood Tests	What They Identify
Acne vulgaris	Testosterone, DHEA-S, SHBG, fasting insulin, IGF-1, LH/FSH	Hormonal excess, insulin resistance, PCOS
Eczema / Atopic dermatitis	Total IgE, specific IgE (allergens), eosinophil count, ANA	Atopic sensitisation, autoimmune overlap
Psoriasis	CRP, ESR, uric acid, lipid panel, HbA1c, liver function	Systemic inflammation, metabolic syndrome, liver
Rosacea	H. pylori antibodies, zinc, vitamin D, cortisol	Gut-skin axis, nutrient deficiencies, stress response
Urticaria (chronic)	TSH, TPO antibodies, ANA, CBC with eosinophils, total IgE	Thyroid autoimmunity, autoimmune urticaria
Generalised itch	LFTs, kidney function, thyroid, ferritin, blood glucose, FBC	Liver/kidney disease, thyroid, iron deficiency, diabetes

For Acne: Hormones, Insulin, and IGF-1

Androgens are the primary hormonal driver of acne. Testosterone and its derivative DHT stimulate sebaceous glands to produce more sebum, which — combined with the shedding of dead skin cells — blocks follicles and creates the environment for Cutibacterium acnes (formerly Propionibacterium acnes) to proliferate. Blood tests for acne should include total and free testosterone, DHEA-S, and SHBG (low SHBG means more free androgens reaching skin receptors).

Insulin and IGF-1 (insulin-like growth factor 1) are underappreciated acne drivers. High-glycaemic diets raise both insulin and IGF-1, which in turn stimulate androgen production in the skin and sebaceous glands independently. Fasting insulin above 7–8 µIU/mL and IGF-1 in the upper quartile for age are associated with worse acne severity. This explains why low-glycaemic diets consistently improve acne in clinical trials — they lower insulin and IGF-1.

For Eczema: IgE, Eosinophils, and Immune Markers

Atopic dermatitis (eczema) is an IgE-mediated inflammatory condition in most cases. Total serum IgE is elevated in the majority of patients with moderate-severe atopic dermatitis — levels above 200–300 IU/mL are common, and values above 1000 IU/mL are seen in severe atopic disease. The degree of IgE elevation correlates roughly with disease severity and with the likelihood of food or environmental sensitisation.

Peripheral eosinophil count (part of the CBC differential) is also typically elevated in atopic dermatitis — often above 0.5 × 10⁹/L in active disease. Markedly elevated eosinophils (above 1.5 × 10⁹/L) warrant investigation for eosinophilic oesophagitis, parasitic infection, or hypereosinophilic syndrome. Specific IgE testing for common allergens (house dust mite, grass pollen, cat, peanut, egg) can identify environmental or dietary triggers contributing to flares.

In adults presenting with eczema for the first time, checking ANA (antinuclear antibodies) is reasonable to exclude lupus or other connective tissue diseases that can produce eczematous rashes. Patch testing (a dermatological procedure, not a blood test) is needed to identify contact allergen triggers.

For Psoriasis: Systemic Inflammation and Metabolic Risk

Psoriasis is now recognised as a systemic inflammatory disease, not merely a skin condition. It is strongly associated with psoriatic arthritis (30% of psoriasis patients), metabolic syndrome, cardiovascular disease, and non-alcoholic fatty liver disease. Blood tests in psoriasis serve two purposes: assessing systemic inflammatory burden and monitoring for metabolic complications.

CRP and ESR reflect overall inflammatory activity and correlate with disease severity. Uric acid is elevated in psoriasis and correlates with severity — hyperuricaemia is found in up to 20% of psoriasis patients, and psoriasis itself is an independent risk factor for gout. A full lipid panel, HbA1c, and liver function tests should be checked annually in psoriasis patients given the metabolic disease burden.

Before starting systemic treatments — particularly methotrexate, which is hepatotoxic — liver function tests and hepatitis B and C serology are mandatory. Before biologic treatments (TNF-alpha inhibitors, IL-17 or IL-23 inhibitors), tuberculosis screening (IGRA or Mantoux test) and hepatitis B serology are required, as these drugs suppress immune surveillance.

Nutrients That Affect Skin Health

Several nutrient deficiencies worsen skin conditions and can be measured with blood tests. Zinc deficiency impairs wound healing and is associated with acne severity — serum zinc below 70 µg/dL is considered low. Vitamin D deficiency is common in eczema and psoriasis patients; supplementation improves outcomes in deficient individuals. Omega-3 index (EPA+DHA in red cell membranes) correlates inversely with inflammatory skin disease severity. Iron deficiency (low ferritin) can cause generalised itch and exacerbate inflammatory conditions through impaired immune regulation.