SALT

What is SALT

The SALT score (Severity of Alopecia Tool) is the percentage of scalp without hair (0–100). Introduced by E. Olsen et al. in 2004, it is the standard measure of alopecia areata and is used to decide on JAK inhibitor treatment and to assess response.

How it is calculated

The scalp is divided into four views with weights: top 40%, back 24%, right side 18%, left side 18%. The hairless share of each view is estimated; SALT = 0.40·top + 0.24·back + 0.18·right + 0.18·left.

Olsen classes: S0 no hair loss, S1 < 25%, S2 25–49%, S3 50–74%, S4 75–99% (S4a 75–95%, S4b 96–99%), S5 100%; B — body, N — nail involvement.

How to read the result

• Severity (King 2022): ≤ 20 mild, 21–49 moderate, ≥ 50 severe; one level higher with eyebrow/eyelash involvement, no response to treatment after ≥ 6 months, diffuse positive pull test, or marked psychosocial impact.
• Response: SALT50/75/90 — 50/75/90% improvement; the treatment goal in trials is SALT ≤ 20 (≤ 20% scalp hair loss), the best response SALT ≤ 10.

Using the calculator

Each view is split into four equal quadrants: set the hairless share of each, or of the whole view at once. Eyebrows and eyelashes are rated on the ClinRO 0–3 scales. Enter the baseline SALT to see percentage improvement and the thresholds reached.

Questions and answers

What does SALT ≤ 20 mean?

No more than 20% of the scalp is without hair. It is the primary goal in trials of JAK inhibitors (baricitinib, ritlecitinib, deuruxolitinib).

Why does the top of the scalp count for 40%?

View weights match their share of scalp area per Olsen 2004: top 40%, back 24%, each side 18%.

Are eyebrows and eyelashes included?

Not in SALT itself, but their involvement (ClinRO ≥ 2) raises severity by one level per King 2022.

References

1. Olsen EA, Hordinsky MK, Price VH, et al. Alopecia areata investigational assessment guidelines — Part II. J Am Acad Dermatol. 2004;51(3):440–447.
2. King BA, Senna MM, Ohyama M, et al. Defining severity in alopecia areata: current perspectives and a multidimensional framework. Dermatol Ther (Heidelb). 2022;12(4):825–834.
3. King B, Ohyama M, Kwon O, et al. Two phase 3 trials of baricitinib for alopecia areata. N Engl J Med. 2022;386(18):1687–1699.