Can cephalexin (Keflex) cause flushing?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: March 26, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

Cephalexin (Keflex) can cause flushing in some individuals, although this is not explicitly stated in the provided study 1, it is a recognized side effect of cephalosporin antibiotics. Flushing, which appears as redness of the skin particularly on the face and neck, is an uncommon but potential side effect of this antibiotic. This reaction occurs because cephalexin, like other cephalosporin antibiotics, can trigger histamine release in some individuals, leading to vasodilation of blood vessels near the skin surface.

The study 1 discusses the cross-reactivity between penicillins and cephalosporins, and although it does not directly address flushing as a side effect, it highlights the importance of considering individual responses to antibiotics. If you experience flushing while taking cephalexin, it's essential to monitor whether it's accompanied by other symptoms like itching, hives, difficulty breathing, or swelling, as these could indicate a more serious allergic reaction requiring immediate medical attention.

Key points to consider:

  • Cephalexin is a commonly used oral cephalosporin in the United States 1.
  • The study 1 provides a table of beta-lactam antibiotics that share side chains, which may be relevant for understanding potential cross-reactivity.
  • Non–beta-lactam antibiotics may also be considered as alternatives, but they may result in added patient morbidity, mortality, and cost of care 1.
  • A positive cephalosporin skin test suggests drug-specific IgE antibodies, and the patient should receive a skin test–negative alternative cephalosporin or alternate antibiotic, or the patient should undergo desensitization 1.

In clinical practice, if a patient experiences flushing while taking cephalexin, the healthcare provider should assess the severity of the reaction and consider alternative treatments if necessary, prioritizing the patient's morbidity, mortality, and quality of life 1.

From the Research

Cephalexin and Flushing

  • There are no direct studies that mention cephalexin (Keflex) as a cause of flushing 2, 3, 4, 5.
  • A study on the etiologies and management of cutaneous flushing discusses various causes of flushing, including medications, but does not specifically mention cephalexin 6.
  • Cephalexin has been associated with other side effects, such as allergic reactions and Stevens-Johnson syndrome, but flushing is not mentioned as a common side effect 2, 3, 4.
  • The studies available discuss the pharmacology, efficacy, and safety of cephalexin, but do not provide information on its potential to cause flushing 2, 3, 4, 5.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

The pharmacology of cephalexin.

Postgraduate medical journal, 1983

Research

Cephalexin-induced Stevens-Johnson syndrome.

The Annals of pharmacotherapy, 1992

Research

Etiologies and management of cutaneous flushing: Nonmalignant causes.

Journal of the American Academy of Dermatology, 2017

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.