Daily or during-attack exposure to a narrow slice of dim green light. Small studies report less light pain, milder attacks, fewer headache days, and better function; a systematic review judged that evidence as very weak. Brighter or mixed-color light can worsen pain and light sensitivity. Add-on with little whole-body risk; benefit remains uncertain; research is financially entangled with the products. (Full Review)

Protocol

Wavelength

525 nm

±10 nm LED strip; target peak 515–535 nm

Intensity

4–100 lux

Dim indoor light in a dark room

Session

1–2 hours daily

10-week preventive block, or about 2 hours during an attack

Time to effect

Photophobia

Minutes

During an attack under dim narrow-band green

Attack-phase pain

10 weeks

Daily 525 nm exposure

Headache days

10 weeks

Daily preventive exposure; not a same-morning preventive

Benefits

High: Less photophobia under dim narrow-band green; lower attack-phase pain with repeated exposure; fewer monthly headache days with daily exposure; better day-to-day function and quality of life

Medium: Shorter headache-phase duration with daily exposure

Low: Better sleep during or after exposure; less anxiety during attacks

Speculative: Lasting analgesia through spinal opioid peptides

Contraindications

Uncontrolled photosensitive epilepsy, especially with a history of flicker- or pattern-triggered seizures

Active untreated retinal disease, recent intraocular surgery, or ophthalmologist-imposed light restriction

People who already find dim narrow-band green painful on a brief test exposure

Key Interactions

Prescription migraine preventives (caution, additive uncertainty)

Acute migraine drugs (monitor) (triptans, gepants, NSAIDs)

Photosensitizing drugs (caution, phototoxic / light-injury risk) (doxycycline, demeclocycline, amiodarone, chlorpromazine)

Opioid analgesics (theoretical, likely minor)

Over-the-counter (OTC) sleep aids and melatonin (monitor if evening use)

Magnesium, riboflavin, coenzyme Q10 (additive, untested)

tDCS and other neuromodulation (additive in one small trial)

Tinted ipRGC-blocking glasses versus adding green (competing, not synergistic by design)

Risk & Side Effects

High: Headache or photophobia intensification when the light is too bright or not narrow-band

Speculative: Evening circadian stimulation; flicker-triggered seizure in photosensitive epilepsy

Monitoring

Marker	Target	Why
Monthly headache days	≥50% reduction from own baseline	Primary endpoint in the 2021 crossover
HIT-6 score	≥6-point drop; functional target often <50	Captures disability, not just day counts
Pain intensity (0–10 numeric rating)	Drop of ≥2 points or ≥30% from baseline	Secondary in 2021
Photophobia rating (0–10 during a standard indoor light)	Stable or falling versus baseline; a rise during a green session is a stop-rule	Directly tracks the High-level harm

Cadence: 4-week baseline diary, HIT-6, and 0–10 pain before first session; repeat at 2 weeks, 4 weeks, and 10 weeks, then every 3 months if daily use continues

Qualitative Assessment

Ability to work, train, and do chores during the week
Sleep onset and night awakenings after session days
Whether other lights or screens leaked into the session
Rescue-drug counts (not a target to drop blindly)

Green Light Therapy to Treat Migraine

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment