# Intralesional Therapy in Dermatology

> Intralesional therapy for NEET-PG Dermatology covers triamcinolone, bleomycin, 5-FU and Candida antigen uses, with their local and systemic adverse effects.

- Canonical URL: https://prepelephant.com/topics/neet-pg/dermatology/intralesional-therapy-in-dermatology
- Exam / course: NEET-PG · Subject: Dermatology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Rook's Textbook of Dermatology; Fitzpatrick's Dermatology; IADVL Textbook of Dermatology
- How to cite: "Intralesional Therapy in Dermatology", PrepElephant, https://prepelephant.com/topics/neet-pg/dermatology/intralesional-therapy-in-dermatology

## Direct answer

Intralesional therapy in dermatology is the injection of a drug directly into a skin lesion to treat it locally while limiting systemic exposure. Triamcinolone is the commonest agent, used for keloids, hypertrophic scars, alopecia areata and lichen planus. Bleomycin, 5-fluorouracil and Candida antigen have further uses, and each carries its own adverse effects that must be understood before injecting.

## What you must remember

- **Triamcinolone:** the mainstay for keloids, hypertrophic scars, alopecia areata, discoid lupus and lichen planus, injected into the lesion.
- **Keloid response:** triamcinolone flattens and softens keloids, but recurrence is common, so it is often combined with other treatment.
- **Bleomycin:** used for warts and selected keloids or tumours, and it causes local pain and necrosis, with systemic toxicity such as pulmonary fibrosis when absorbed.
- **5-fluorouracil:** used for keloids, warts and some superficial lesions, and it causes local irritation and pain.
- **Candida antigen:** used intralesionally for warts, with a local immune response meant to clear the virus.
- **Atrophy and telangiectasia:** repeated steroid injection can thin the skin and produce visible vessels.
- **Technique:** dilute corticosteroid suspensions and inject into the dermis at the lesion margin to limit atrophy.

## A stepwise approach to intralesional injection

Intralesional therapy is safe when the indication, the drug and the dose are matched to the lesion. The steps below reflect routine clinic practice in dermatology.

1. **Confirm the diagnosis:** make sure the lesion is one that responds to injection, such as a keloid or patchy alopecia, and not a lesion needing biopsy first.
2. **Choose the agent:** triamcinolone for inflammatory or fibrotic lesions, bleomycin or 5-FU for selected warts and keloids, and Candida antigen where its use is indicated.
3. **Prepare the dose:** use the lowest effective concentration and volume, since higher doses increase atrophy and systemic effects.
4. **Inject the dermis:** place the needle into the dermis at the lesion margin and inject slowly, to limit tissue damage.
5. **Plan the interval:** space injections at intervals set by the response, commonly several weeks apart.
6. **Warn and review:** explain pain, possible atrophy and pigmentary change, and review at each visit for recurrence or complications.

Good technique matters as much as drug choice, because the complications of intralesional therapy are largely local and technique-dependent.

## Where the exam tries to catch you

Intralesional questions test the agent-indication link and the local complications of each drug.

- **Trap:** using triamcinolone as the first answer for every keloid recurrence — **Correct:** recurrence is common, so triamcinolone is often combined with excision, cryotherapy or other adjuncts.
- **Trap:** injecting high-dose triamcinolone into a thin area — **Correct:** repeated high-dose steroid causes atrophy and telangiectasia, so the lowest effective dose is used.
- **Trap:** attributing bleomycin's risks only to the skin — **Correct:** bleomycin has systemic toxicity, including pulmonary fibrosis, so the total dose and exposure matter.

## Frequently asked questions

### Which lesions are commonly treated with intralesional triamcinolone?
Intralesional triamcinolone is commonly used for keloids, hypertrophic scars, alopecia areata, discoid lupus erythematosus and lichen planus. It works by local suppression of inflammation and fibroblast activity. Repeat injections are usually spaced at intervals set by the response.

### What are the main adverse effects of intralesional corticosteroid injection?
Intralesional corticosteroid injection commonly causes skin atrophy, telangiectasia and pigmentary change at the injection site. Pain during injection and transient flushing are also reported. Systemic absorption is limited, but repeated high-dose injections can cause HPA suppression.

### Why is 5-fluorouracil used intralesionally?
5-fluorouracil is used intralesionally for selected warts, keloids and superficial lesions because it inhibits DNA synthesis in proliferating cells. Its local effects include pain, inflammation and ulceration at the site. Dose and interval are chosen with the lesion size and the patient's tolerance in mind.

### How does Candida antigen work in warts?
Candida antigen is injected into warts to provoke a local immune response, which may help clear the virus in some patients. The response is thought to be cell-mediated. It is one of several options for warts and is chosen according to the lesion and the clinician's experience.