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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medically reviewed by WellAlly Editorial TeamLast reviewed October 19, 2026Editorial policy
Medication15 min read

Patient Guide to Cephalexin (Keflex) for Skin Infections

Published: October 19, 2026Updated: October 19, 2026

Cephalexin is a widely prescribed oral antibiotic used to treat bacterial skin and soft tissue infections like cellulitis, impetigo, and folliculitis. This guide explains how to properly take your medication, monitor your healing, manage side effects, and recognize when to contact your healthcare provider.

Quick Summary

Take cephalexin consistently on an evenly spaced schedule, finish the entire prescribed course, and monitor your skin for signs of spreading infection or allergic reaction.

Important Medical Disclaimer

This guide is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with qualified healthcare providers for medical concerns.

Step-by-Step Guide

1

Establish an Evenly Spaced Dosing Schedule

Cephalexin works best when a consistent amount of the drug remains in your bloodstream. Depending on your prescription, you will typically take a dose every 6 hours or every 12 hours. Set daily alarms on your phone or align doses with routine daily events to prevent missing a dose.

Important: If you miss a dose, take it as soon as you remember, but skip it if it is almost time for your next scheduled dose. Never double up on pills.

2

Take With or Without Food

You can take cephalexin capsules or tablets on an empty stomach or with meals. If you experience mild nausea or stomach discomfort after taking a dose, taking the medication with food or a glass of milk often reduces gastrointestinal irritation. Swallow capsules whole with a full glass of water.

3

Track the Margin of Skin Redness

Before or shortly after starting cephalexin, use a surgical or ballpoint pen to gently draw a line along the outer edge of the red or inflamed skin. This creates a visual baseline so you and your clinician can objectively measure whether the infection is shrinking or spreading. Check the area twice daily under good lighting to monitor changes in swelling and warmth.

Important: Seek emergency medical attention if redness rapidly expands far beyond your drawn line, if red streaks travel toward your heart, or if you develop high fever and chills.

4

Complete the Entire Prescribed Duration

Most uncomplicated skin infections require a 5- to 10-day course of cephalexin. Even if your skin redness, swelling, and pain improve noticeably within the first 48 to 72 hours, stopping early allows surviving bacteria to multiply and potentially develop resistance. Finish every single dose unless an adverse reaction forces your doctor to discontinue it.

5

Differentiate Normal Side Effects from Complications

Mild side effects such as slight nausea, mild stomach cramps, or occasional loose stools can happen and are usually manageable. However, severe watery diarrhea that persists multiple times a day may signal a serious secondary bowel infection known as Clostridioides difficile. Contact your clinic promptly if diarrhea is severe, bloody, or accompanied by intense abdominal cramping.

Important: Do not take anti-diarrheal medications like loperamide (Imodium) without speaking to your doctor first, as they can trap harmful bacterial toxins in the gut.

6

Store the Medication Securely

Store cephalexin capsules and tablets at room temperature between 68°F and 77°F (20°C to 25°C), away from excess heat, moisture, and direct light. Avoid keeping your medication in humid bathroom cabinets. If you were prescribed a liquid oral suspension, store it tightly closed in the refrigerator and discard any leftover liquid after 14 days.

Important: Keep all medications out of the reach and sight of young children and pets.

Frequently Asked Questions

Can I take cephalexin if I have a penicillin allergy?
It depends on the severity and nature of your reaction. Cephalexin is a cephalosporin, and while true cross-reactivity with penicillin is low (around 1% to 2%), people who have experienced severe, life-threatening reactions to penicillin (such as anaphylaxis, facial swelling, or breathing difficulty) should generally avoid it unless cleared by an allergist or their prescribing physician.
How quickly should my skin infection begin to improve?
Most patients notice initial improvement—such as reduced warmth, less tenderness, and stabilization of redness—within 48 to 72 hours of starting cephalexin. If your symptoms continue to worsen after 48 hours or do not improve by day three, inform your provider, as your infection may require a different antibiotic or drainage.
Can I drink alcohol while taking cephalexin?
Cephalexin does not have a dangerous chemical interaction with alcohol like some other antibiotics (such as metronidazole), but consuming alcohol is not recommended. Alcohol can exacerbate common side effects like nausea, dehydration, and dizziness, and may impede your immune system's ability to clear the skin infection.
Does cephalexin treat MRSA skin infections?
No. Cephalexin is effective against Methicillin-Susceptible Staphylococcus aureus (MSSA) and Streptococcus species, but it is not active against Methicillin-Resistant Staphylococcus aureus (MRSA). If a skin culture reveals MRSA or your infection fails to respond, your doctor will switch you to an antibiotic effective against resistant strains.
  1. 1
    Mayo ClinicSource
  2. 2
    National Health Service (NHS)Source
  3. 3
    NIH DailyMedSource
  4. 4
    Centers for Disease Control and Prevention (CDC)Source

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed October 19, 2026. · Read our editorial policy