Safer sex – how can I prevent STIs?

Practising safer sex can protect you from getting, or passing on, sexually transmitted infections (STIs) and also reduces the risk of unplanned pregnancy. However, it is impossible for any method to be 100% effective, which is why it is called ‘safer sex’ rather than safe sex.

This page focuses on preventing STIs. For more information about preventing pregnancy, see contraception.

Who is at risk of sexually transmitted infections (STIs)?

STIs are really common. Anyone who is sexually active is at risk of getting an STI. You're most at risk if you have a new sexual partner or don't use a barrier method of contraception, such as a condom, when having sex.

Other things that increase the risk of unsafe sex are:

  • being drunk (which may lead to you not using a condom)
  • using recreational drugs
  • feeling pressured to have sex
  • thinking that it’s okay ‘just this once’
  • believing that you can tell if someone has an STI because they will have symptoms.

How can I prevent STIs?

Vaginal or anal sex

Using condoms during vaginal or anal sex with every partner, every time, is the best way to prevent STIs. Condoms offer the best available protection against STIs by acting as a physical barrier to prevent the exchange of semen, vaginal fluids or blood between partners.

However, condoms need to be used correctly, to offer the best available protection. Condoms must be put on properly and must be used from the start of sex to the very end as STIs can be transmitted via pre-ejaculate (fluid from the penis that comes out before ejaculation). 

Sex using a condom may still spread an infection if the condom does not fully cover the infected area. For example, some infections such as pubic lice, scabies, genital warts, herpes and syphilis are spread by close skin-to-skin contact. Condoms provide some protection against these STIs, but not full protection as they do not cover the entire genital skin area. Read more about condoms and how to use them properly

Remember that you have the right to say no to sex if your partner doesn’t want to use a condom.

Oral sex

Many STIs, as well as other infections, can be spread through oral sex. If you put your mouth in contact with your partner’s penis, you need to use a condom to avoid STIs. If you put your mouth in contact with your partner’s anus or vulva (outside of your vagina) while having sex, you need to use a dental dam (whether you are a guy or girl). This is especially important if you’ve got a cut or sore around your mouth or lips or bleeding gums.

Sex toys

Many STIs can also be transmitted by using sex toys. You can avoid STIs by:

  • keeping sex toys clean – wash them after each use
  • covering penetrative sex toys, such as vibrators, with a new condom each time they're used
  • not sharing sex toys
  • having a different set of sex toys for each partner.

Other tips for safer sex

  • Have sex with only one partner, when neither of you has any STIs, is the safest way to have sex.
  • Avoid having sex if you or your partner have any symptoms – such as sores, ulcers, lumps/bumps, discharge or any pain around the genital or anal area – get checked by a doctor first.
  • Have regular STI checks (every 3 months), especially if you have had any unprotected sex (sex without a condom) or have more than one partner.
  • Wash your hands with soap and water before and after sex or sexual play.
  • Don't brush your teeth within 30 minutes or so of sexual play because it can irritate your gums and create small cuts that increase your chances of getting an infection (use mouthwash or sugar-free gum if you want to freshen your breath).
  • Never have sex (even with a condom) if your partner has a visible sore, ulcer or lump on their genitals or anal area. Suggest they see their doctor or visit a sexual health clinic.
  • Be prepared for safe sex – it doesn’t have to be a passion killer. Carry condoms in your wallet or purse and keep them handy at home so you don’t have to interrupt sex to look for one. 
  • Learn how to use condoms. They may take a little getting used to, but it’s better than catching an STI. Water-based lubricants are best to reduce the risk of the condom breaking during sex.
  • Educate yourself about STIs. Anyone who has sex is at risk. Don’t think you can tell if someone has an STI just by looking at them. Most STIs don’t have any obvious signs.
  • Be mature about STIs and reassure yourself and your partner that an STI is not a moral judgement of character, but an infection like any other. Having an STI does not mean that you are ‘dirty’ or ‘cheap’.
  • Have STI tests if you are in a relationship and you want to have sex without a condom. Both partners should be tested. Think of STI testing as a sign of respect for each other.

Are there any safe sexual activities?

There are a few sexual activities that carry a low risk of STI transmission because they don't involve the exchange of semen, vaginal fluids or blood between partners. These include: 

  • kissing, although recent studies have shown that deep throat kissing (French kissing) may be associated with the spread of gonorrhoea
  • cuddling
  • massage
  • masturbation
  • mutual masturbation.

What should I do if I have had unsafe sex?

If you have had unsafe sex take the following steps:

  • Avoid vaginal or rectal ‘douching’ (washing out or irrigating these areas with water or other fluids) as the irritation to delicate tissues could increase the risk of infection.
  • Make sure you are not at risk of pregnancy. Consider taking the emergency contraceptive pill within 72 hours is best, but it can be taken with 120 hours of unprotected sex (including if there was a broken condom or if no other form of contraception was used).
  • See your doctor or visit a sexual health clinic promptly to be tested for STIs. Some STIs take 2 weeks to become positive with testing, so you may need to come back for follow-up testing.
  • Consider post-exposure prophylaxis (PEP) to prevent HIV, if you are a man who has had unprotected anal intercourse with another man. 

Learn more

Safer sex and condoms Ministry of Health, NZ
What is safer sex? Just The Facts, NZ
Should I have a sexual health check? Health Promotion Agency and Ministry of Health, NZ, 2013

Reviewed by

Dr Phoebe Hunt is currently working as a registrar in sexual health at ADHB. Her interests are in women’s health, sexual health and lifestyle medicine. Phoebe is planning on starting GP training next year.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Phoebe Hunt, Auckland DHB Last reviewed: 20 May 2020