Every summer, the same question comes up in clinics and patient forums: I am injecting an anticoagulant into my abdomen morning and evening, my energy has improved a little, and my child has a school holiday. Can I go into the sea? Behind the question there are usually two feelings at once — guilt about a summer spent indoors, and fear that something will go wrong far from the hospital.
It helps to clear up one misunderstanding first. Low-molecular-weight heparin (LMWH) given as a subcutaneous injection is used to treat or prevent blood clots, that is, venous thromboembolism (VTE). Water does not wash the medicine out, and it does not seep into the injection site. What actually decides the answer is not the water itself but what happens to the body in it. Four factors are worth separating.
The first is bleeding. While you are anticoagulated, the same knock produces a much larger bruise and a small cut bleeds longer. So the risk lies in the events, not the swimming: being knocked over by waves, slipping on wet rocks or steps, collisions on water slides or tubes, diving and surfing. A blow to the head deserves the most caution, because it can look harmless at first and declare itself hours later. Standing in shallow water or walking slowly in a calm area belongs to a different category altogether.
The second is your skin and anything attached to your body. If you have a surgical wound that has not fully healed, a drain, or a central line such as a chemoport or PICC, then showering and immersing your body in water are treated very differently — immersion is the stricter one. Sea water, rivers, lakes, hot springs and outdoor pools each carry different organisms and different standards of hygiene. In people with liver disease or reduced immunity, sea-water bacterial infections are uncommon but can progress quickly, so an open wound or an access site must be reviewed before you soak. Bruising or pinpoint bleeding at the injection site is usually fine to get wet; an open or weeping wound is not.
The third is where the clot itself sits in time. Someone newly diagnosed and taking a full treatment dose twice a day is in a different position from someone stable months later. Swelling in one leg, calf pain, breathlessness on mild exertion or chest discomfort means a medical review comes before travel plans. Long journeys themselves raise clot risk, so build in a stop every hour or two to stand, walk and move your ankles.
The fourth is heat and the treatment calendar. Outdoor activity in extreme heat causes dehydration, and dehydration brings dizziness and haemoconcentration. If you are also receiving chemotherapy, put your travel dates next to the period when your white cell count is expected to be lowest (often somewhere around days 7 to 14 after a dose, though this varies by regimen). Some chemotherapy drugs and recent radiotherapy also make skin far more sensitive to sunlight.
A few practical points about travelling with injections. Prefilled syringes are generally stored at room temperature and kept away from high heat, so avoid a parked car in midsummer or a bag in direct sun, and do not let them rest directly against an ice pack. Pack more doses than the number of days, bring a rigid container for used needles, and carry a prescription or a short letter confirming the medication. Keep your usual interval between doses where possible. After swimming, dry thoroughly and inject into clean skin; afterwards press gently rather than rubbing, and leave a gap before hot baths or strenuous activity.
In the clinic, asking in this order tends to produce concrete answers even in a short appointment. One: is my current dose treatment or prophylaxis? Two: what are my recent platelet and haemoglobin levels, and am I in a higher-bleeding-risk period? Three: if I have a wound, drain or central line, may it be immersed, and does it need a waterproof dressing? Four: which dates this month are safest? Five: if a problem arises away from home, who do I contact and what should I show them?
Seek medical care without waiting for any of the following: bleeding that does not stop after ten minutes of pressure, a bruise or swelling that keeps enlarging, black stools or red urine, repeated nosebleeds or gum bleeding, sudden swelling and pain in one leg, sudden breathlessness, chest pain or fainting, headache, vomiting or confusion after a head injury, or a fever of 38°C or higher.
Finally, a summer with your child is not made only in the water. Dipping your feet in the shade early in the morning or late in the afternoon, short spells in and out with rest between, an evening walk instead of a full day at a water park — these still leave the season behind. Planning around the day after, rather than filling one day completely, usually buys more time together in the end.
This article provides general information and does not replace medical care. Recommendations differ according to the specific drug and dose, the state of any wound or device, and your treatment schedule, so please discuss travel and swimming plans with your own healthcare team in advance.