Antiseptics

Introduction

“Have you washed your hands?” – a question that you may come across quite a lot.

Germs and dirt exist in the natural environment. We may come across different germs (e.g. bacteria, viruses, fungi, etc.) in our daily life. Our skin is the best natural barrier to protect our body from the outside invasion. Nevertheless, we need to clean ourselves regularly in order to keep away from the foul (and possibly the accumulated pathogens) affecting our health and the ease of living. Bathing or a thorough handwashing is the most effective way of eliminating dirt from our body. In our daily activities, our “hands” are the first-line “contact” with the outside world (e.g. touching utensils and surfaces of public installations). If we do not want to be the culprit of spreading germs, it is necessary to clean the hands regularly and properly. Whether or not our hands are visibly soiled, washing our hands regularly with liquid soap and water is an effective way to keep our hands hygienic and prevent ourselves from contracting diseases. An alcohol-based sanitizer (in the form of a handrub) is an effective alternative if our hands are not visibly soiled.

The difference between antiseptics and disinfectants

Antiseptics and disinfectants both kill microorganisms, but there is a big difference between antiseptics and disinfectants in their applications. Antiseptics are often meant for skin cleansing and wound management, while disinfectants are for cleaning of non-living surfaces, such as countertops and handrails. Both antiseptics and disinfectants contain chemical agents that are sometimes called biocides. Chemical structures of active ingredients of antiseptics and disinfectants vary, as well as their mechanisms of action. In general, these compounds possess a wide spectrum of antimicrobial activity and they act on different parts of the microorganism, e.g. cell membrane, cell walls, cell contents or enzymes, etc. Each type of chemicals may have a distinct profile on pathogens, meaning some may work better on some pathogens and/or under specific pH environments, but not on the others. Whether the product is regarded as an antiseptic or a disinfectant will depend on the chemical structure of its active ingredient(s), the concentration, the formulation, and the proposed use. Taking alcohol as an example, alcohol can be used as a “skin antiseptic” e.g. swabbing our skin before injection, or it can also be used to “disinfect” non-living surfaces, e.g. trolleys, forceps, thermometers, etc.

Both antiseptics and disinfectants are very useful in eliminating germs. In this article, we will be focusing on “antiseptics”.

Common antimicrobial agents used as antiseptics

Alcohol

Alcohols (ethanol 70% or isopropyl alcohol around 70%) are effective antiseptics and disinfectants. They act rapidly and evaporate quickly. Both ethanol and isopropyl alcohol are often used in skin cleansing before injection or skin puncture, and are equally effective in cleaning and disinfecting surfaces. They are also active ingredients in handrub or in sanitizers for hand hygiene.

Chlorhexidine

Chlorhexidine is often used in handwashing products due to its low skin irritability and works well in alkaline environment. Because of its residual effect (even after rinsing), chlorhexidine is a useful tool for surgeons cleansing their hands before operations. In addition, preparations of special formulations containing chlorhexidine (with ethanol or specialized detergent) can be used in preoperative and postoperative skin cleansing for patient.

Chlorhexidine is used as an ingredient in some mouthwash preparations, while sterile chlorhexidine solution can be used in cleansing wounds or skin injuries.

Iodine

Iodine tincture has often been used as a skin antiseptic. Povidone-iodine (a form of iodine forms a polymer complex with povidone) is commonly used in products for preoperative skin cleansing and in the management of some contaminated wounds. However, iodine antiseptics usually have unpleasant odour and may stain clothing.

Antiseptics for Consumers

There are many products with antiseptics available in the market. Some of which are also used in the clinical settings. For example, preoperative hand cleansing, wound management by healthcare providers, etc.

Antiseptics that are more commonly used by the general consumers are available in form of liquids (such as detergent for hands) and solids (such as medicated soap with antibacterial ingredients). Apart from the “rinsing-off” products, some consumer antiseptics offer the “leave-on” option (e.g. wipes, hand-sanitizers). That means the antiseptics are allowed to be left on the skin, without requiring rinsing off with water.

Nevertheless, these kinds of products may not be much more effective than simple washing with soap and adequate water. The consumer antiseptics (such as hand-sanitizers) could be an alternative where the soap and water is not available.

In general, antiseptics for consumer-use purpose should NOT be applied to wounds or broken skin. Products marketed for wounds management are required to meet more stringent microbiological standards. Pharmaceutical products manufactured for cutaneous use should not exceed microbial limits specified in pharmacopoeia, and products manufactured for wound irrigation or for use on broken skin must be sterile. Sterile products are usually labelled with the word “Sterile”.

Are antiseptics safe and what are the precautions when using antiseptics?

Adverse reaction/precautions

Antiseptics can be used to kill or inhibit the growth of microorganisms. However, some antiseptics may cause skin irritation. Allergic reactions such as hives, reddening, or swelling of tissues may also occur when using some antiseptics. Extra care should be given when applying antiseptics to children because “chemical burns” can happen. The use of antiseptic in newborn babies is not recommended unless under the instructions of healthcare professionals.

Avoid excessive use of antiseptics. Do not pool antiseptics into skin folds, or soak them into occlusive dressing materials. Inappropriate use can damage skin and may even be toxic.

Microbial Contamination

Antiseptics kill or inhibit the growth of germs, but each antiseptic may have its own antimicrobial profile. That means, there may be germs that are resistant to some antiseptics.

Taking chlorhexidine as an example, it is a chemical ingredient that possesses a broad antimicrobial spectrum. However, some studies showed that opportunistic bacteria, such as Burkholderia cepacia complex, Achromobacter, and Ralstonia, may contaminate the chlorhexidine products. These kinds of “opportunistic” bacteria will usually not do any harm to healthy persons. But if the contaminated product is applied to patients with weakened immunity, chronic lung diseases (e.g. cystic fibrosis) or on renal/peritoneal dialysis, it may cause severe infections to them.

Consumers are recommended to read the product information carefully for any precautions after opening. For sterile products (e.g. sterile solutions for irrigation), the contents have to be used immediately after opening (i.e. breaking the seal). Any unused contents have to be discarded.

Storage of Antiseptics

Improper storage will spoil the chemical quality of antiseptics. Taking chlorhexidine as an example, it tends to break down at raised temperature, especially in alkaline conditions.

In general, antiseptics should be stored indoor, away from direct sunlight, and at room temperature. Before application, inspect whether there are any unexpected features of the products (e.g. the irrigation solutions should be free from foreign matters). Do not use the product if in doubt.

Alternatives to Antiseptics

Antiseptics help kill germs and prevent possible infections. Nevertheless, they are not perfect and have their own limitations.

Observance of hand hygiene is definitely a good practice. Maintaining a healthy lifestyle, paying attention to other aspects of personal hygiene (e.g. cough etiquette and wear a mask when having respiratory symptoms), keeping a living environment hygienic and ensuring up-to-date vaccination status, are also simple and direct ways to keep away from many infectious diseases.

Skin is the primary barrier for stopping foreign pathogens attacks. If we have wounds (i.e. the skin is broken), the principle is to prevent infection, promote healing, and minimize further injury. Clean up the wound and then protect it with dressing or bandages with aseptic technique. For wound without infection, simple cleansing with sterile normal saline (0.9% sodium chloride solution) will usually suffice. On the other hand, antiseptics may instead cause pain, irritation, or allergy. For severe cases (e.g. deep wound with mud, dirt, or rust), seek medical attention for proper management.

Sterile normal saline is a commonly used cleansing fluid. As it is similar to human body fluid, it does not irritate wound tissues and causes less pain when applied. Antiseptics may irritate the wound or cause an allergic reaction. Generally, a non-infected wound could be cleansed with normal saline and antiseptics are not required, while an infected wound must be managed according to a doctor's instructions.
For more information on wound care, please visit https://www.elderly.gov.hk/english/healthy_ageing/home_safety/wound_care.html.

Regulation of Antiseptics in Hong Kong

To safeguard public health in the safe and proper use of skin antiseptic products, under the current regulatory control of pharmaceutical products with antiseptic ingredients, skin antiseptic products containing benzalkonium salts, benzethonium salts, cetrimide, chlorhexidine, hydrogen peroxide and iodine/povidone iodine that fulfil the definition of pharmaceutical product must be registered with the Pharmacy and Poisons Board of Hong Kong, a statutory body established under the Pharmacy and Poisons Ordinance (PPO) (Cap. 138), before they can be legally sold in Hong Kong.

Summary

Antiseptics are products containing chemical agents that can kill or inhibit the growth of microorganisms. Nevertheless, they are not for universal usage, for example, in the prevention of infectious diseases.

We need to maintain a healthy lifestyle and practise good hygiene. Observance of hand hygiene is the easiest and most effective option to prevent the spread of infectious diseases. For more information about proper hand hygiene, please visit the dedicated webpage of the Centre for Health Protection of the Department of Health at https://www.chp.gov.hk/en/healthtopics/content/460/19728.html

Acknowledgement: The Drug Office would like to thank the Centre for Health Protection (CHP) for their valuable contribution to the preparation of this article.