For patients and clinicians: this article explains what happens in a cortisone injection for acne. Injectable steroids are prescription-only and must be given by a trained clinician. Injecting yourself risks infection, permanent dents and skin discolouration.
The short answer
- Usual concentration for acne cysts: 2.5 mg/mL triamcinolone acetonide (range about 2–5 mg/mL).
- How it’s made: Kenalog-10 (10 mg/mL) diluted 1:3 with sterile 0.9% saline (or lidocaine) = 2.5 mg/mL; Kenalog-40 diluted 1:15.
- Volume: typically 0.05–0.1 mL per cyst, injected into the cyst, not under it.
What a cortisone shot for acne does
An intralesional steroid injection delivers a potent anti-inflammatory directly into an inflamed nodule or cyst. Within one to three days the swelling and pain usually fall dramatically, which is why people seek it before an event or when a deep cyst is very painful. It doesn’t prevent new cysts; for recurring nodular acne, a dermatologist will look at longer-term treatment such as oral antibiotics, hormonal therapy or isotretinoin.
The steroid usually used is triamcinolone acetonide (Kenalog-10, Kenalog-40). It’s a suspension of small crystals, which is why it must be shaken well before use, and why too concentrated a dose can stay in the skin and cause atrophy.
Dilution table
| Target concentration |
From Kenalog-10 (10 mg/mL) |
From Kenalog-40 (40 mg/mL) |
Typical use |
| 2.5 mg/mL |
0.25 mL + 0.75 mL diluent (1:3) |
0.1 mL + 1.5 mL diluent (1:15) |
Acne cysts, facial lesions |
| 5 mg/mL |
0.5 mL + 0.5 mL (1:1) |
0.125 mL + 0.875 mL (1:7) |
Thicker nodules, alopecia areata |
| 10 mg/mL |
Undiluted |
0.25 mL + 0.75 mL (1:3) |
Hypertrophic scars, some keloids |
| 20–40 mg/mL |
— |
Undiluted or 1:1 |
Keloids, by specialists |
Diluents are sterile 0.9% sodium chloride for injection or lidocaine 1% (which reduces sting). Bacteriostatic saline containing benzyl alcohol is used in some clinics for adults. Mixed syringes are drawn up just before use and shaken because the crystals settle quickly. Professional notes on mixing and syringes are in our clinical pharmacy notes.
Results and side effects
| What |
When / how often |
| Less pain and swelling |
Within 24–72 hours |
| Cyst flattened |
About 3–7 days |
| Skin dent (atrophy) |
Uncommon at 2.5 mg/mL; more likely with higher strength or volume; often improves over months |
| Lightened skin (hypopigmentation) |
More noticeable on darker skin; usually temporary |
| Small visible blood vessels, infection |
Rare |
The same principle is used for keloid and hypertrophic scars, at higher strengths and often in a series of injections every 4–6 weeks. Results there are gradual: scars soften and flatten over several sessions.
Other options for a painful cyst
- A warm compress several times a day.
- Don’t squeeze or pick deep cysts; it pushes inflammation deeper and scars.
- Topical treatments (benzoyl peroxide, adapalene) help prevent new spots but don’t shrink a cyst quickly.
- See a GP or dermatologist if cysts recur or scar; effective treatments exist. Our skin treatments guide explains retinoids and steroid strengths.
Frequently asked questions
Can Kenalog be injected into the nose or a nose piercing bump?
Clinicians sometimes inject low-strength triamcinolone into keloids, including on the ear or nose. A piercing bump is often not a keloid and may resolve with care; have it assessed before any injection.
How long does a cortisone shot for a cyst last?
The treated cyst usually doesn’t come back, but new cysts can form elsewhere. The steroid itself is active in the skin for a few weeks.
What do Kenalog scar injections look like before and after?
Raised, red or itchy scars typically become flatter, softer and less itchy over 2–4 sessions. Over-treatment can leave a depression or pale patch, so clinicians start with low doses and space sessions.
Sources and further reading
CanforaMedicine Guide
