Drug & supplement interaction

Light Therapy + Phenytoin

Phenytoin brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, and others.

No Known Interaction
The bottom line No known interaction

We found no known interaction between Light Therapy and Phenytoin in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Light Therapy and Phenytoin

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Phenytoin and Light Therapy in our sources. This does not guarantee that the combination is completely free of risk — research on Light Therapy alongside specific medications may be limited.

Light Therapy is a treatment rather than something you take. Tell whoever provides it which medicines you use, and ask your prescriber whether it is appropriate for your health and treatment. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Light Therapy safety at a glance

Light Therapy overall Use caution Generally well tolerated, but certain eye, skin, and mood conditions need medical guidance.
Pregnancy Possibly Safe When bright light therapy is used short-term. Other types of light therapies, especially PUVA, have not been extensively evaluated in pregnancy or lactation. On... Read the full pregnancy detail
Breastfeeding Possibly Safe When bright light therapy is used short-term. Other types of light therapies, especially PUVA, have not been extensively evaluated in pregnancy or lactation. On... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Phenytoin and Light Therapy? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Phenytoin

Interactions in our licensed database are recorded against drug classes, not just single drug names. Phenytoin is filed under 14 classifications — including cytochrome p450 2c8 (cyp2c8) substrates, cytochrome p450 2c9 (cyp2c9) inducers, anticonvulsants. Light Therapy has documented interactions with 1 drug class — the most serious being photosensitizing drugs (moderate) — and none of Phenytoin’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Light Therapy Does Interact With Other Medications

Light Therapy has 335 moderate known drug interactions in our database — Phenytoin isn’t one of them. If you take anything else, check it against the full list below.

Taking anything else?

Check Another of Your Medications Against Light Therapy

Covers the 2,830 medications we’ve checked against Light Therapy. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Light Therapy and Phenytoin May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so having Light Therapy while taking the medicine can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Tremor or shakiness / Headache Additional detail

    Light Therapy

    “Headache, decreased sex drive, tremor, and trouble falling asleep have been reported in patients receiving light therapy. Exposure to light therapy for more than 24 hours as an infant is linked to higher odds of development delays in the domains of communication, gross motor, problem solving, and personal-social skills by 3 years of age.”

    Light Therapy · Natural Medicines adverse-effect record, reported in cluster headache.

    6 sources cited
    1. 28931. Tuunainen, A., Kripke, D. F., and Endo, T. Light therapy for non-seasonal depression. Cochrane Database Syst Rev 2004;(2):CD004050. DOI
    2. 28936. Chesson, A. L., Jr., Littner, M., Davila, D., Anderson, W. M., Grigg-Damberger, M., Hartse, K., Johnson, S., and Wise, M. Practice parameters for the use of light therapy in the treatment of sleep disorders. Standards of Practice Committee, American Acade DOI
    3. 28979. Terman, M. and Terman, J. S. Bright light therapy: side effects and benefits across the symptom spectrum. J Clin Psychiatry 1999;60(11):799-808. DOI
    4. 106586. Nussbaumer-Streit B, Thaler K, Chapman A, et al. Second-generation antidepressants for treatment of seasonal affective disorder. Cochrane Database Syst Rev 2021;3(3):CD008591. PubMed
    5. 109264. Donmez M, Yorguner N, Kora K, Topcuoglu V. Efficacy of bright light therapy in perinatal depression: A randomized, double-blind, placebo-controlled study. J Psychiatr Res 2022;149:315-322. PubMed
    6. 109271. Sun W, Yan J, Wu J, Ma H. Efficacy and safety of light therapy as a home treatment for motor and non-motor symptoms of Parkinson disease: A meta-analysis. Med Sci Monit 2022;28:e935074. PubMed

    Phenytoin

    Listed in the ADVERSE REACTIONS section of the FDA label for Phenytoin. Read the label on DailyMed ›

  • Anxiety or restlessness Additional detail

    Light Therapy

    “Light therapy may cause agitation, and rarely hypomania or mania. Jumpiness, jitteriness, nervousness, irritability, anxiety, delusions, and aggressive behavior has been reported in patients with dementia.”

    Light Therapy · Natural Medicines adverse-effect record, reported in anxiety.

    4 sources cited
    1. 28931. Tuunainen, A., Kripke, D. F., and Endo, T. Light therapy for non-seasonal depression. Cochrane Database Syst Rev 2004;(2):CD004050. DOI
    2. 28936. Chesson, A. L., Jr., Littner, M., Davila, D., Anderson, W. M., Grigg-Damberger, M., Hartse, K., Johnson, S., and Wise, M. Practice parameters for the use of light therapy in the treatment of sleep disorders. Standards of Practice Committee, American Acade DOI
    3. 28979. Terman, M. and Terman, J. S. Bright light therapy: side effects and benefits across the symptom spectrum. J Clin Psychiatry 1999;60(11):799-808. DOI
    4. 106586. Nussbaumer-Streit B, Thaler K, Chapman A, et al. Second-generation antidepressants for treatment of seasonal affective disorder. Cochrane Database Syst Rev 2021;3(3):CD008591. PubMed

    Phenytoin

    Listed in the ADVERSE REACTIONS section of the FDA label for Phenytoin. Read the label on DailyMed ›

  • Constipation Additional detail

    Light Therapy

    “Nausea is a commonly reported side effect of light therapy. Changes in appetite, dry mouth, diarrhea, constipation, and abdominal pain have also been reported.”

    Light Therapy · Natural Medicines adverse-effect record, reported in constipation.

    3 sources cited
    1. 28938. Morgan, M. and Khan, D. A. Therapeutic alternatives for chronic urticaria: an evidence-based review, Part 2. Ann Allergy Asthma Immunol 2008;100(6):517-526. PubMed
    2. 28979. Terman, M. and Terman, J. S. Bright light therapy: side effects and benefits across the symptom spectrum. J Clin Psychiatry 1999;60(11):799-808. DOI
    3. 106586. Nussbaumer-Streit B, Thaler K, Chapman A, et al. Second-generation antidepressants for treatment of seasonal affective disorder. Cochrane Database Syst Rev 2021;3(3):CD008591. PubMed

    Phenytoin

    Listed in the ADVERSE REACTIONS section of the FDA label for Phenytoin. Read the label on DailyMed ›

  • Nausea Additional detail

    Light Therapy

    “Phototherapy seems to be well tolerated when used appropriately.

    Most Common Adverse Effects:

    Mild burning, nausea, phototoxicity, pruritus, and redness.

    Serious Adverse Effects (Rare):

    Hypomania or mania, skin cancers such as squamous cell carcinoma.”

    Light Therapy · Natural Medicines adverse-effect record, reported in nausea and vomiting.

    Phenytoin

    Listed in the ADVERSE REACTIONS section of the FDA label for Phenytoin. Read the label on DailyMed ›

Reported for Light Therapy but not commonly for Phenytoin: a change in sex drive, blurred vision, stomach pain and eye irritation or redness.

Effects for Phenytoin come from the ADVERSE REACTIONS section of its FDA label; effects for Light Therapy come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Light Therapy in Pregnancy & Breastfeeding

Pregnancy And Lactation Possibly Safe

When bright light therapy is used short-term. Other types of light therapies, especially PUVA, have not been extensively evaluated in pregnancy or lactation. One preliminary study suggests that PUVA use does not result in teratogenic effects. Until more information is available, avoid use in those who are pregnant and lactating.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

From our Q&A

Questions About Light Therapy or Phenytoin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Light Therapy or Phenytoin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Phenytoin

This page covers Light Therapy only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenytoin page lists 224 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 9 major · 187 moderate · 28 minor.

From our pharmacist’s overview on the Phenytoin page

“Phenytoin (Dilantin) is a seizure medicine with a narrow therapeutic index, meaning small changes in its blood level can bring seizures back or tip over into toxicity, so I treat its supplement list with real seriousness. The biggest group, 78 ingredients, piles on sedation, and alcohol, kava, and GHB all rate major for exactly that re…”

Reviewed by 2 · Jul 18, 2026

Open the Phenytoin interaction page

How much people look this up

Where Light Therapy and Phenytoin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Light Therapy
Steady interest

#882 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Phenytoin
Top half

#781 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Light Therapy reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Light Therapy and Phenytoin records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Treatment approach

About Light Therapy

What is Light Therapy?

  • Seasonal affective disorder (SAD)
  • Non-seasonal depression
  • Sleep and circadian rhythm problems
  • Jet lag and shift-work sleep issues
  • Certain skin conditions

Light therapy uses controlled exposure to bright artificial light and is best supported for seasonal affective disorder, where it is a recognized treatment option. It is generally safe for most people when used as directed, but you should talk to a doctor or pharmacist first, especially if you have eye conditions, bipolar disorder, or take medicines that increase light sensitivity.

Not applicable (light exposure, not a plant) · Light boxes, dawn-simulating alarm clocks, light visors, wearable light devices, blue/red light panels

An interaction check asks whether these two react with each other — it does not ask whether Light Therapy is a good idea for someone in your situation. Here is what our Light Therapy record says about it on its own.

Light Therapy: dosing

There is no single dose that fits everyone, and the right approach depends on the device and the reason you are using it. For seasonal affective disorder, a common general approach involves a 10,000-lux light box used for a set time in the morning, sitting a recommended distance from the light with eyes open but not staring at it.Because brightness, distance, and timing all matter, follow the instructions that come with your specific device. They can help you pick the right device and schedule.

From our Light Therapy monograph — the full record covers uses, side effects and every documented interaction.

Read the full Light Therapy monograph & all interactions
Medication

About Phenytoin

What Is Phenytoin Used For?

Brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, Dilantin injection

Phenytoin is used to treat and prevent seizures. The specific types covered depend on the formulation. Oral extended-release capsules (including Phenytek), chewable tablets (including Dilantin Infatabs and Phenytoin Infatabs), and oral suspension (including Dilantin-125) are used for tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures; most oral forms also cover prevention and treatment of seizures occurring during or after neurosurgery. Chewable tablets and some capsule formulations also cover complex partial seizures.

Parenteral (injectable) phenytoin sodium is used for generalized tonic-clonic status epilepticus (a prolonged, life-threatening seizure emergency) and for prevention and treatment of seizures during neurosurgery. The IV form can also substitute short-term for oral phenytoin when a patient cannot take it by mouth.

Most-Reported Side Effects for Phenytoin

From FAERS, the FDA’s public side-effect reporting system (40,278 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Convulsion 3,522 reports
Seizure 3,095 reports
Toxicity to various agents 1,888 reports
Fall 1,604 reports
Dizziness 1,539 reports
See full Phenytoin drug information
Keep checking

Other Drugs & Light Therapy

Browse every other medication we’ve checked against Light Therapy — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
335Moderate
0Minor
2,494No known interaction
Moderate

335 interactions

Showing 60 of 335 moderate interactions — see all 335 on the Light Therapy page.

No interaction 2,494 drugs checked — show the list
Evidence & sources

Light Therapy References

The 35 references that drive our Light Therapy monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Meduri, N. B., Vandergriff, T., Rasmussen, H., and Jacobe, H. Phototherapy in the management of atopic dermatitis: a systematic review. Photodermatol Photoimmunol Photomed 2007;23(4):106-112. PubMed
  2. Kumar, P., Chawla, D., and Deorari, A. Light-emitting diode phototherapy for unconjugated hyperbilirubinaemia in neonates. Cochrane Database Syst Rev 2011;(12):CD007969. PubMed
  3. Pathirana, D., Ormerod, A. D., Saiag, P., Smith, C., Spuls, P. I., Nast, A., Barker, J., Bos, J. D., Burmester, G. R., Chimenti, S., Dubertret, L., Eberlein, B., Erdmann, R., Ferguson, J., Girolomoni, G., Gisondi, P., Giunta, A., Griffiths, C., Honigsmann
  4. Beani, J. C. and Jeanmougin, M. [Narrow-band UVB therapy in psoriasis vulgaris: good practice guideline and recommendations of the French Society of Photodermatology]. Ann Dermatol Venereol 2010;137(1):21-31.
  5. Leon, A., Nguyen, A., Letsinger, J., and Koo, J. An attempt to formulate an evidence-based strategy in the management of moderate-to-severe psoriasis: a review of the efficacy and safety of biologics and prebiologic options. Expert Opin Pharmacother 2007; PubMed
  6. Kroft, E. B., Berkhof, N. J., van de Kerkhof, P. C., Gerritsen, R. M., and de Jong, E. M. Ultraviolet A phototherapy for sclerotic skin diseases: a systematic review. J Am Acad Dermatol 2008;59(6):1017-1030. PubMed
  7. Tuunainen, A., Kripke, D. F., and Endo, T. Light therapy for non-seasonal depression. Cochrane Database Syst Rev 2004;(2):CD004050. DOI
  8. Chesson, A. L., Jr., Littner, M., Davila, D., Anderson, W. M., Grigg-Damberger, M., Hartse, K., Johnson, S., and Wise, M. Practice parameters for the use of light therapy in the treatment of sleep disorders. Standards of Practice Committee, American Acade DOI
  9. Morgan, M. and Khan, D. A. Therapeutic alternatives for chronic urticaria: an evidence-based review, Part 2. Ann Allergy Asthma Immunol 2008;100(6):517-526. PubMed
  10. Lee, E., Koo, J., and Berger, T. UVB phototherapy and skin cancer risk: a review of the literature. Int J Dermatol 2005;44(5):355-360. PubMed
  11. Murase, J. E., Lee, E. E., and Koo, J. Effect of ethnicity on the risk of developing nonmelanoma skin cancer following long-term PUVA therapy. Int J Dermatol 2005;44(12):1016-1021. PubMed
  12. Morison, W. L., Baughman, R. D., Day, R. M., Forbes, P. D., Hoenigsmann, H., Krueger, G. G., Lebwohl, M., Lew, R., Naldi, L., Parrish, J. A., Piepkorn, M., Stern, R. S., Weinstein, G. D., and Whitmore, S. E. Consensus workshop on the toxic effects of long
  13. Stern, R. S. The risk of squamous cell and basal cell cancer associated with psoralen and ultraviolet A therapy: a 30-year prospective study. J Am Acad Dermatol 2012;66(4):553-562. PubMed
  14. Stern, R. S. and Lunder, E. J. Risk of squamous cell carcinoma and methoxsalen (psoralen) and UV-A radiation (PUVA). A meta-analysis. Arch Dermatol 1998;134(12):1582-1585. PubMed
  15. Swerdlow, A. J. and Weinstock, M. A. Do tanning lamps cause melanoma? An epidemiologic assessment. J Am Acad Dermatol 1998;38(1):89-98. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Having Light Therapy While Taking Phenytoin: Common Questions

Is it safe to have Light Therapy while taking Phenytoin?
We do not list a known interaction between Light Therapy and Phenytoin. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Light Therapy and Phenytoin have any of the same side effects?
Yes — our sources link each of them separately to 5 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Light Therapy and Phenytoin combination checked?
Interactions in our licensed database are recorded against drug classes. Phenytoin is filed under 14 classifications, and Light Therapy has documented interactions with 1 drug class — none of Phenytoin's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Light Therapy interact with any other medications?
Yes. Light Therapy has 335 documented drug interactions in our database — Phenytoin is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Phenytoin interact with any supplements?
Yes. Phenytoin has documented interactions with 224 supplements in our database — Light Therapy is not one of them. The Phenytoin interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Phenytoin and Light Therapy?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.