Blue Light Therapy vs Cortisone Injection

Blue Light Therapy: Visible blue light, around 415 nm, shone on the skin for mild inflammatory acne. No drug, no ultraviolet, and no downtime. It is not photodynamic therapy, which applies a drug first and is a far stronger treatment.

Cortisone Injection: A tiny shot of diluted steroid into one inflamed acne cyst. It flattens that spot in a few days. It treats the bump, not the acne.

Reviewed by Dr. Schwarz, Board-Certified Dermatologist
Last updated: 10/22/2026

Editorial illustration for Blue Light Therapy, based on the entry’s treatment or equipment reference.

Editorial illustration for Cortisone Injection, based on the entry’s treatment or equipment reference.

Choose if Key differences What is it?What it treats Treatment areas Skin tones How it works Before your treatment Day of treatment After your treatment Risks Cost Questions Related

Choose Blue Light Therapy if…

Choose for mild inflammatory acne when you want a painless, drug-free add-on with no downtime — expect modest results.

Mild red spots, not blackheads
You want to avoid medicines
You can attend twice a week

Choose Cortisone Injection if…

Choose for one painful acne cyst that needs to flatten fast, or for keloids and patchy hair loss.

A single painful cyst before an event
A raised keloid
A patch of alopecia areata

Fine together

Can you have both?

A cortisone injection can calm a single painful cyst at any point during blue light treatment.

Key differences

● Blue Light Therapy

● Cortisone Injection

DowntimeNone → 2+ weeks

None

PainMinimal → Needs anesthesia or sedation

Minimal

Mild

Results showImmediately → 3+ months

1–3 months

Within days

How long it lastsWeeks → Years or permanent

Weeks

Visits neededOne → Every few months

A longer series (4–6+)

Every few months

Cost per visit$ → $$$$$

ReversibleYes, can be undone → No, permanent

No, wears off

No, permanent

What is it?

Blue Light Therapy

Cortisone Injection

What is it?

It means two different treatments.

It can be light alone for acne or part of photodynamic therapy.

The evidence differs.

Discomfort, results and aftercare vary between them.

Ask about medicines.

A photosensitizing medicine changes the treatment.

Aftercare differs.

Light avoidance is needed after photodynamic therapy.

It is injected into a lesion.

An intralesional steroid calms local inflammation or scarring.

It differs from joint injections.

It is not a systemic steroid treatment.

The diagnosis matters.

Infected or uncertain lesions should not be injected.

Side effects can last.

Skin thinning, fat loss and pigment change may persist.

What it treats

Evidence level

Blue Light Therapy

Cortisone Injection

Strong evidenceMost established uses

Actinic Keratosis

Activates PDT medicine for sun damage.

Acne

Flattens a painful cyst within days.

A raised, smooth, firm scar on the upper chest on light skin. It is shiny pink-red and hairless, and its edges spread well past the small mark it grew from.

Keloids

Softens and flattens raised scars.

Alopecia Areata

Regrows hair in patches.

Moderate evidenceSome supportive research

—

A smooth, dome-shaped lump about two centimetres across on the upper back on pale skin, with a tiny dark pore at its center and faintly pink skin over it.

Epidermal Inclusion Cyst

Calms an inflamed cyst.

Limited evidenceEarly or small studies

Acne

Modest reduction in inflamed spots.

—

Not effective

Acne Scarring

Doesn't change scars.

dark keratin plugs in dilated pores on the nose and adjacent left cheek, with the face turned to the person’s right on light skin.

Blackheads

Doesn't clear clogged pores.

Blackheads

Not for clogged pores.

Can make it worse

—

Acne Scarring

Can cause dents in skin.

Treatment areas

Face; the selected area depends on the concern and treatment plan.

The specific lesion, scar or affected patch determines the treatment site; there is no fixed body distribution.

Skin tones

Skin tone

● Blue Light Therapy

● Cortisone Injection

Lighter skin

Low risk

No ultraviolet.

Low risk

A small dent is possible.

Medium skin

Low risk

No pigment change expected.

Some risk

Lighter patches can show.

Deeper skin

Low risk

No pigment change expected.

Some risk

Lightening and dents are more visible; low doses help.

How it works

Blue Light Therapy

Cortisone Injection

How it works

Blue Light Therapy mechanism diagram. Blue light reaches the skin: A selected light regimen exposes the treatment area. Bacterial porphyrins absorb light: Reactive molecules can damage susceptible acne bacteria. Inflammatory acne may improve: Response varies; blue light alone is different from drug-assisted PDT.

Cortisone Injection mechanism diagram. Medicine is placed in a lesion: A clinician injects an appropriate corticosteroid preparation. Inflammatory signaling decreases: The steroid reduces local immune and inflammatory activity. The lesion may soften or flatten: Response depends on the condition, dose, and placement.

Diagram explanation

Blue light reaches the skin: A selected light regimen exposes the treatment area. Bacterial porphyrins absorb light: Reactive molecules can damage susceptible acne bacteria. Inflammatory acne may improve: Response varies; blue light alone is different from drug-assisted PDT.

Schematic illustration. Technique and response vary. This explains a mechanism and does not specify treatment settings.

Medicine is placed in a lesion: A clinician injects an appropriate corticosteroid preparation. Inflammatory signaling decreases: The steroid reduces local immune and inflammatory activity. The lesion may soften or flatten: Response depends on the condition, dose, and placement.

Schematic illustration. Technique and response vary. This explains a mechanism and does not specify treatment settings.

Before your treatment

Blue Light Therapy

Cortisone Injection

2–4 weeks before

Before you book: What is included: Ask whether a drug goes on the skin first.

Not specified

The week before

Not specified

Do not pick: Do not pick, squeeze or heat the spot.

Day of treatment

Blue Light Therapy

Cortisone Injection

Before you arrive

Clean face: Makeup, sunscreen and thick moisturizer block the light.

Clean face: Come with a clean, bare face.

Clean skin: Wash your face and skip makeup on the area.

Arrival & prep

Skin is cleansed.

The provider checks that the spot is an inflamed acne cyst and not a boil.

Treatment

Opaque goggles go on, the panel sits a few inches from your face, and the light runs 10 to 20 minutes.

Very bright even through closed eyelids, and mildly warm. It does not hurt. A mild headache or eye strain afterward happens occasionally, usually from loose goggles.

The skin is wiped with alcohol.

A very fine needle goes just into the bump and a small amount of fluid goes in, under 10 seconds per spot. The sting is sharp for a few seconds, worse if the cyst is already tender, but most people rate it lower than they expect. Numbing does not help much — the needle stick is the whole procedure.

Before you leave

Skin may look slightly flushed for an hour.

A tiny red dot, sometimes a small raised bleb that flattens within an hour.

After your treatment

Blue Light Therapy

Cortisone Injection

First 24 hours

Days 1 to 2: Slight dryness or tightness.

After photodynamic therapy: A drug on the skin first changes everything — several days of redness, swelling and peeling, and no daylight for about 48 hours.

Days 1 to 2: The bump softens and the ache fades.

Days 2–7

Not specified

First few days: A pinprick mark, sometimes a small bruise, fading over a few days.

Days 3 to 7: Most cysts are flat.

Weeks 2–4

Weeks 1 to 2: Inflamed spots settle faster.

Not specified

Time to results

4–8 weeks

24–48 hours for a cyst

How long results last

Weeks to months

Treats only that spot

Risks

Darkening
Persistent redness or stinging
Headaches or eye strain after sessions
A rash after sessions
Long term

Dent in the skin
Lighter patch of skin
Visible small vessels

Cost

Per session

In the US, blue light alone is one of the cheapest in-office treatments, often an add-on to a facial or sold in packages, commonly well under $100 a session.

Roughly $50 to $250 per office visit in the US, usually billed as an office visit plus a procedure charge rather than per spot.

Insurance

Insurance almost never covers blue light for acne, which counts as cosmetic.

Insurance often covers it, since acne cysts count as medical rather than cosmetic.

Questions

Blue Light Therapy

Cortisone Injection

Individual Questions

Is blue light therapy the same as photodynamic therapy?

No, and this is the most common mix-up. Photodynamic therapy puts a photosensitizing drug on the skin and waits an hour or more before the light. That drug causes several days of redness, swelling and peeling. Blue light alone has no drug and no downtime.

Does it work for acne?

For small inflamed spots, modestly. Trials show fewer inflamed lesions over several weeks. It does little for blackheads and whiteheads, does not reach cysts, and is weaker than benzoyl peroxide.

How long does it take to see anything?

Studies measure change at four to twelve weeks with two sessions a week. Eight weeks is a fair test.

Is it safe for eyes?

The devices are bright, which is why goggles are used. Keep them on the whole session, and ask about eye protection if you have a retinal condition or past eye surgery.

Can I use it with a home LED mask?

Yes, though doing both at once adds little. A home device used consistently is often more practical than a course of appointments, and the LED light therapy page covers that evidence.

Will it help my melasma?

No, and it may make it worse. Visible light drives pigment in skin prone to melasma, which needs pigment treatment and daily tinted mineral sunscreen.

How fast does a cortisone shot work on a cyst?

Softening begins within 24 to 48 hours and most spots are flat by day three to five. That figure traces back to one small 1983 trial — it matches what dermatologists see but has never been tested at scale. The mark left behind takes weeks longer, and the injection does not speed that up.

Will it leave a dent?

It can. A shallow depression happens when the dose is too strong, so a lower concentration is the main protection. It is uncommon — most dermatologists see it in well under one patient in a hundred — and it often fills in over several months. But it is not reliably temporary. About half the clinicians who do see it report it lasting more than six months, and occasionally it is permanent. That is why you ask what concentration is being used.

Can I get one before an event?

Yes, the most common reason people ask. Aim for three to five days ahead so the swelling has time to drop. A same-day injection rarely looks better by that evening.

Does it stop acne from coming back?

No. It treats only the spot it is injected into. Preventing the next cyst needs a daily treatment plan, and the guidelines call this an add-on.

Is it safe on deeper skin tones?

Yes. The risk is a lighter patch at the site, more noticeable and slower to fade on deeper skin tones. A lower concentration reduces it, so ask.

Is this approved for acne?

Not in the United States, strictly speaking. The FDA labeling lists intralesional use for keloids, alopecia areata, discoid lupus and others. Acne is not on it. Off-label use for an acne cyst is routine, legal and recommended by the American Academy of Dermatology, but almost nobody says it out loud. In the UK, NICE withdrew its recommendation in 2026 after UK-licensed triamcinolone injections stopped being available — a supply and licensing decision, not a safety one.

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