What the label lists and what reports show
Ritlecitinib side effects
Ritlecitinib's FDA label: “Most common adverse reactions (incidence ≥1%) are headache, diarrhea, acne, rash, urticaria, folliculitis, pyrexia, atopic dermatitis, dizziness, blood creatine phosphokinase increased, herpes zoster, red blood cell count decreased, and stomatitis.” FAERS holds 1,862 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is headache (87 reports).
- No generic listed
- Boxed warning
Check it at the source: the ritlecitinib FDA label on DailyMed (effective June 17, 2026, Pfizer Laboratories Div Pfizer Inc); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of LITFULO?LITFULO may cause serious side effects, including: See " What is the most important information I should know about LITFULO? " The most common side effects of LITFULO include: • headache • diarrhea • acne • rash • hives • inflamed hair pores (folliculitis) • fever • eczema • dizziness • shingles • decreased red blood cell counts • mouth sores, redness and swelling of the lining of your mouth These are not all the possible side effects of LITFULO. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. You may also report side effects to Pfizer at 1-800-438-1985.
Source: FDA drug label, Pfizer Laboratories Div Pfizer Inc, effective June 17, 2026 (SPL set 6b2f9446-fb23-4741-b73a-5a2f993733c3), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (incidence ≥1%) are headache, diarrhea, acne, rash, urticaria, folliculitis, pyrexia, atopic dermatitis, dizziness, blood creatine phosphokinase increased, herpes zoster, red blood cell count decreased, and stomatitis.
Table 2. Adverse Reactions in Clinical Trials of LITFULO for the Treatment of Alopecia Areata Reported in ≥1% of subjects and at a higher rate than placebo for up to 24 weeks.
| Reaction | LITFULO 50 mg N=130 n (%) | Placebo N=213 n (%) |
|---|---|---|
| Headache Headache includes headache and migraine. | 14 (10.8) | 18 (8.5) |
| Diarrhea Diarrhea includes diarrhea and frequent bowel movements. | 13 (10.0) | 8 (3.8) |
| Acne Acne includes acne and acne pustular. | 8 (6.2) | 10 (4.7) |
| Rash Rash includes rash and dermatitis allergic. | 7 (5.4) | 2 (0.9) |
| Urticaria | 6 (4.6) | 3 (1.4) |
| Folliculitis | 4 (3.1) | 4 (1.9) |
| Pyrexia | 4 (3.1) | 0 |
| Dermatitis atopic | 3 (2.3) | 1 (0.5) |
| Dizziness | 3 (2.3) | 3 (1.4) |
| Blood creatine phosphokinase increased | 2 (1.5) | 0 |
| Herpes zoster | 2 (1.5) | 0 |
| Red blood cell count decreased | 2 (1.5) | 0 |
| Stomatitis | 2 (1.5) | 0 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are described elsewhere in the labeling: • Serious Infections [see Warnings and Precautions (5.1) ] • Malignancy and Lymphoproliferative Disorders [see Warnings and Precautions (5.3) ] • Thromboembolic Events [see Warnings and Precautions (5.5) ] • Hypersensitivity [see Warnings and Precautions (5.6) ] • Laboratory Abnormalities [see Warnings and Precautions (5.8) ] Most common adverse reactions (incidence ≥1%) are headache, diarrhea, acne, rash, urticaria, folliculitis, pyrexia, atopic dermatitis, dizziness, blood creatine phosphokinase increased, herpes zoster, red blood cell count decreased, and stomatitis. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer Inc. at 1-800-438-1985 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The safety of LITFULO was evaluated in three randomized, placebo-controlled clinical trials and one long-term trial in subjects with alopecia areata, including alopecia totalis and alopecia universalis, who were 12 years of age and older. …
Source: FDA drug label, Pfizer Laboratories Div Pfizer Inc, effective June 17, 2026 (SPL set 6b2f9446-fb23-4741-b73a-5a2f993733c3), via openFDA; the full label on DailyMed
What do FAERS reports show?
1,862 reports list ritlecitinib among the medicines taken, each a report of something that happened, not proof the medicine caused it; 3 are coded as a death and 86 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 17 reactions below, 8 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Ritlecitinib: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions