Corticosteroids switch off the signals that drive inflammation. They also slow down fibroblasts, the cells that lay down collagen. Those two effects explain almost everything this injection is used for.
When inflammation is the problem — an angry acne cyst, a hidradenitis nodule, a thick psoriasis plaque, the immune attack on hair follicles in alopecia areata — the steroid shuts the reaction down locally within a day or two, and the swelling, redness and pain settle. When excess collagen is the problem — a keloid or a hypertrophic scar — the steroid slows new collagen production and speeds up the breakdown of what is already there, so the scar gradually softens, flattens and stops itching.
The reason it is injected rather than swallowed is dose. The amount used here is a fraction of what a tablet delivers, and it stays largely where it is put, so you avoid the effects that come with steroids taken by mouth. The trade is that it only treats what the needle reaches. Injecting one lump does nothing for the next one.
That same local action is also where the side effects come from. Steroid slows collagen production in normal skin too, and it can thin the fat just under the injection site. That is what produces a dent.
Almost nothing is required, which is part of why this is often done at the same appointment as the consultation.
Eat beforehand. Feeling faint is the most common problem during a small injection and an empty stomach makes it likelier.
Tell your provider if you are pregnant, breastfeeding, have diabetes, or have had a steroid injection anywhere in the last few weeks.
Tell them if you have ever had a dent or a pale patch at an injection site. That changes the concentration they choose.
Ask for numbing cream if you are anxious, and be aware it needs 30 minutes on the skin to work. For most sites people skip it, because the injection is over before the cream would have helped.
There is no need to stop blood thinners, fast, or arrange a lift home.
This is a short procedure with a short unpleasant part, and knowing where that part sits makes it much easier.
You sit or lie down. The area is wiped with alcohol, which is cold. The provider draws up a small amount of medicine — usually well under 1 mL, sometimes only a fraction of that — into a small syringe with a very fine needle. They may stretch the skin taut with their fingers, or press an ice pack or a vibrating device beside the site, both of which genuinely blunt the sensation.
The needle goes in. The prick itself is minor, roughly like a flu shot or less. The part that stings is the fluid going in, and it stings because the medicine is being forced into tissue that has no room for it — particularly in a keloid, which is dense. Expect a strong burning, stretching pressure that builds over a few seconds and eases quickly once the needle comes out.
A fair description: it is a sharp, hot ache lasting five to ten seconds per injection site. That is the worst part of the entire procedure, and it is brief. Most people who were dreading it say afterwards that the wait was worse.
For a keloid you may feel the resistance as the plunger is pushed. Sometimes several small injections are made across one scar rather than one big one, so the medicine spreads evenly. Each is another few seconds.
For alopecia areata the scalp is injected in a grid of tiny pricks, often ten to thirty of them across a patch. Each one is small, and the scalp is less sensitive than people expect, but the number is what people remember.
The site goes white or blanched immediately — that is normal and settles in an hour. A small bump under the skin where the fluid sits is also normal and flattens within a day. There may be a spot of blood; a plaster goes on and comes off the same day.
The injections themselves take one to three minutes. A single acne cyst is 30 seconds. A whole scalp of patches might be ten minutes. The appointment is usually 10 to 20 minutes in total.
Yes, immediately. There is no sedation and nothing that impairs you. People go back to work straight afterwards.
There is no real recovery, but there is a sequence.
Mild soreness or a bruised ache at the site. The skin may look blanched or white where the medicine went in, which resolves. Paracetamol if you need it, and most people do not.
An acne cyst or a hidradenitis lump usually starts settling within 24 to 48 hours — the pain goes before the lump does. A small bruise may appear, especially on the face or if you take a blood thinner.
A keloid or hypertrophic scar starts to itch less first, then to soften. Visible flattening takes longer than people expect and does not really begin until after the second injection.
A psoriasis plaque or a granuloma annulare ring flattens over two to six weeks.
Regrowth in an alopecia areata patch typically shows at eight to twelve weeks after the first injection, often as fine white hairs that pigment up later.
Nothing. Wash normally the same day, exercise the same day, no dressing needed beyond a plaster for an hour. There is no wound to look after, which is the main practical advantage this has over every other procedure on this list.
Acne cyst: pain settles within a day, the lump usually flattens in two to four days. One injection is normally all that is needed for that spot.
Hidradenitis nodule: relief within one to two days. It treats that lump only — it does not slow the disease down or prevent the next one.
Keloids and hypertrophic scars: injections every four to six weeks, usually three to six of them. Itch and tenderness improve first, often after one session. Flattening is gradual and partial — the realistic goal is a softer, flatter, less symptomatic scar rather than skin that looks untouched. Studies put meaningful improvement at roughly 50 to 100 percent of keloids treated, with recurrence in a substantial minority within a year or two. Many people need maintenance injections, and pairing steroid with pressure, silicone or surgery gives better durability than steroid alone.
Alopecia areata: regrowth at about eight to twelve weeks, repeated every four to six weeks while patches are active. It regrows the patch you inject. It does not stop new patches appearing, and alopecia areata can relapse regardless.
Psoriasis plaque or granuloma annulare: flattening over two to six weeks, and the patch often stays clear for months. Psoriasis tends to return to the same spots eventually.
The honest summary: this treatment reliably improves what you inject, on a timescale of weeks, and it does not change the underlying condition. Anything driven by an ongoing process — keloid tendency, alopecia areata, hidradenitis, psoriasis — will keep producing new lesions.
There is no home version of this, and that is worth being clear about because the gap between the two is wide.
Steroid creams and ointments — even strong prescription ones like clobetasol — barely penetrate a keloid or a thick plaque. They work on the surface. Injection places the medicine inside the tissue. For a raised scar, a cream may reduce itch a little and will not flatten it.
What does have a real place at home:
Silicone sheets or gel, used on a new or existing raised scar for at least 12 hours a day over two to three months. This is the best-evidenced self-treatment for scars, and it works better started early.
Pressure — an earring-style pressure clip after keloid removal on the earlobe, or a pressure garment. Slow, unglamorous, and effective.
Steroid tape or plaster (flurandrenolide tape) on prescription, which is closer to an injection than a cream because it holds the medicine against the scar under occlusion.
What not to do: over-the-counter kits sold for injecting anything at home, and anything that involves cutting, burning or tying off a lump yourself. Tying a thread around a growth cuts off its blood supply and it does often fall off — along with a real risk of infection, a worse scar than the growth, and a lesion that nobody ever examined. Some of what people remove at home turns out to be a skin cancer, and destroying it removes the chance to diagnose it. Get it looked at first.