What is the orange stuff they put on before surgery? Unpacking the science of surgical prep

September 21, 2025 •

4 min read

According to the CDC, surgical site infections are a serious risk, with hundreds of thousands of cases occurring annually in the U.S.. To dramatically reduce this risk, hospitals rely on powerful antiseptics, including the orange stuff they put on before surgery, to cleanse the skin and protect the patient.

Quick Summary

The orange antiseptic applied before surgery is typically a solution containing povidone-iodine, a substance that kills germs to prevent infections. However, some solutions containing chlorhexidine may also be used, which are dyed for visibility during application.

Key Points

Povidone-Iodine: The orange liquid is often povidone-iodine (Betadine), an iodine-based antiseptic that kills a broad range of germs.
Chlorhexidine: A potent antiseptic, often dyed orange for visibility, is a modern alternative that provides a faster and longer-lasting antimicrobial effect.
Key Purpose: The main goal of surgical prep is to reduce the microbial count on the patient's skin, which is the primary source of surgical site infections.
Drying is Crucial: Alcohol-based antiseptics, like those containing chlorhexidine, must be completely dry before surgery to avoid fire risks.
Allergy Alert: Though rare, allergic reactions to both iodine and chlorhexidine are possible. Patients should inform their doctor of any known allergies to antiseptics.
Enhanced Safety: Preoperative skin preparation is a cornerstone of modern infection control, significantly improving patient outcomes and safety.

The two most common surgical antiseptics

While the sight of a healthcare provider painting a patient's skin with a bright orange solution is a familiar image, the substance isn't always the same. There are two primary types of antiseptic agents commonly used for surgical skin preparation: povidone-iodine and chlorhexidine. Both are highly effective at killing microorganisms on the skin's surface to prevent surgical site infections (SSIs), a crucial step in modern medical care.

Povidone-iodine: The classic orange solution

Povidone-iodine (PVP-I) is an iodophor, which is a complex of iodine and a carrier polymer. The well-known brand name for this antiseptic is Betadine. Its golden-brown, or orange, color is natural to the povidone-iodine complex itself and is a clear indicator that it has been applied.

Mechanism of action: Povidone-iodine works by slowly releasing free iodine into the solution, which kills cells through the iodination of lipids and oxidation of cytoplasmic and membrane compounds. This broad-spectrum activity is effective against bacteria, viruses, and fungi.
Application: Often applied in a multi-step process, it requires sufficient contact time with the skin to release the free iodine and achieve its antimicrobial effect. Its efficacy can be reduced by the presence of organic matter, such as blood.
Benefits: It offers a broad spectrum of antimicrobial activity and is suitable for most skin surfaces.

Chlorhexidine: The modern powerhouse

Chlorhexidine gluconate (CHG) is another powerful antiseptic, often formulated with alcohol to increase its efficacy. Brand names include ChloraPrep and Hibiclens. While the solution itself is often colorless, dyes are frequently added to produce a vibrant orange or sometimes pink hue, making it easy to see where it has been applied.

Mechanism of action: CHG works by disrupting the bacterial cell membrane, which causes the cell contents to leak and the bacteria to die. Its positive charge is attracted to the negative charge of bacterial cells, contributing to a rapid kill rate.
Sustained activity: A key advantage of CHG is its persistent antimicrobial effect. It binds to the stratum corneum (the outermost layer of the skin), allowing it to provide continued protection for several hours after application, unlike iodophors, which lose their efficacy as they dry.
Considerations: While highly effective, CHG should not be used on open wounds, near the eyes or ears, or in the genital region, and it requires adequate drying time to prevent chemical burns.

Comparison of surgical antiseptics

When choosing an antiseptic for a procedure, healthcare professionals consider several factors, including the type of surgery, the patient's allergies, and the duration of the antimicrobial effect required. This table highlights some key differences between povidone-iodine and chlorhexidine:


Feature	Povidone-Iodine (PVP-I)	Chlorhexidine Gluconate (CHG)
Mechanism	Releases free iodine to oxidize and kill microbes	Disrupts bacterial cell membranes
Onset of Action	Intermediate, requires longer contact time	Rapid, especially with alcohol
Duration of Effect	Effective for a shorter period, neutralized by organic matter	Sustained and persistent activity for hours
Visible Color	Naturally golden-brown/orange	Often dyed orange, though colorless formulations exist
Suitability	Broad application, including mucosal areas	Should not be used near eyes, ears, or on open wounds
Relative Efficacy	Proven, effective antiseptic	Often considered superior in preventing SSIs when alcohol-based

The importance of surgical skin preparation

Surgical site infections are a significant risk, and the largest source of pathogens is often the patient's own skin flora. The goal of skin preparation is to reduce this microbial load to an absolute minimum, ensuring a sterile surgical field. This process is far more sophisticated than simply wiping the skin. It is a critical component of infection control protocol, alongside sterile instruments and proper hand hygiene, that helps minimize postoperative complications.

What to expect from surgical prep

Before arriving for surgery, patients are often instructed to shower with an antimicrobial soap, such as chlorhexidine, for a specified number of days. This helps to reduce the baseline bacterial population on the skin. In the operating room, the antiseptic is applied to the surgical site using a non-touch technique, starting at the incision area and moving outwards. For alcohol-based preparations, allowing proper time for the solution to completely dry is essential, as this minimizes the risk of fire. The antiseptic is a visible and reassuring step in the comprehensive approach to ensuring a successful and safe surgical outcome.

Understanding the science behind the preparation

The development of modern surgical antisepsis, influenced by figures like Joseph Lister in the 19th century, represents a monumental leap in medical safety. What may seem like a simple paint application is actually a carefully planned and executed procedure designed to protect patients from potentially life-threatening infections. The science behind the orange stuff they put on before surgery is a testament to the meticulous standards of modern medicine, ensuring that every precaution is taken to safeguard the health of those undergoing a procedure.

For more information on the effectiveness of different antiseptic agents in preventing surgical site infections, you can review landmark studies like the one published in the New England Journal of Medicine that compared chlorhexidine and povidone-iodine. [Source of authority link to NEJM article on antiseptic comparison: https://www.nejm.org/doi/full/10.1056/NEJMoa0810988]

In conclusion

Whether it's the classic povidone-iodine or the more persistent chlorhexidine, the orange liquid used for surgical prep is a vital defense against infection. It's a key part of the comprehensive sterile procedures that have transformed surgery from a high-risk endeavor into a routine, safe medical practice. Understanding what this solution is and why it's used provides patients with greater peace of mind as they head into the operating room.

Frequently Asked Questions

No, it is not always the same. While povidone-iodine is a common orange antiseptic, other solutions containing chlorhexidine are also used and are often dyed orange to make the application area visible.

Antiseptic is applied over a large area to ensure that all potential bacteria are eliminated from the surgical field. This prevents microorganisms from the surrounding skin from migrating toward the incision during the procedure.

No, the orange stain is temporary. The povidone-iodine will eventually wash off the skin and does not cause permanent discoloration.

If the antiseptic contains alcohol, allowing it to dry completely is a critical safety step to prevent fire. Alcohol is flammable and must evaporate fully before any electrical or heating instruments are used.

Patients with a known allergy to iodine or chlorhexidine must inform their healthcare team. In such cases, alternative non-allergenic antiseptics, like benzalkonium chloride, are used for skin preparation.

Clinical studies have shown varied results, but many suggest that alcohol-based chlorhexidine preparations may offer more sustained antibacterial activity and better protection against SSIs in some surgeries. Both, however, are effective antiseptics.

Yes, many hospitals require patients to shower with an antimicrobial soap, such as chlorhexidine, before surgery. This helps reduce the normal bacterial flora on the skin before the hospital's final antiseptic application.