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What Causes Sudden Mood Swings in an 18-Month-Old?

author image Michelle Kulas
Michelle Kulas worked in the health-care field for 10 years, serving as a certified nurses' assistant, dental assistant and dental insurance billing coordinator. Her areas of expertise include health and dental topics, parenting, nutrition, homeschooling and travel.
What Causes Sudden Mood Swings in an 18-Month-Old?
18 month old laying on floor after temper tantrum. Photo Credit: Marina Dyakonova/iStock/Getty Images

One minute, your 18-month-old may be happily playing, and the next, she might be flailing on the floor in the grips of a temper tantrum. You may wonder what happened to your sweet baby, and whether you are entering the territory of the Terrible Twos, albeit a few months early. While toddlerhood can be a challenge to both you and your child, you may be able to reduce her mood swings in some cases. Tantrums and moodiness are age appropriate, and understanding the reasons why she's cranky can help you cope with her transition from babyhood into childhood.

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Language Frustration

Your 18-month-old may be able to say some words, but he might not be able to express all of his wants and needs. When pointing and attempting to speak does not result in understanding, his frustration may cause him to go from happy to angry and frustrated within a matter of seconds. While his communication skills will improve markedly over the next year, you can teach him some simple baby signs to help in the meantime, recommends's Dr. Jay L. Hoecker. Teaching hand signals for common requests, including "drink," "more," "hungry" and "sleep" may help alleviate some of his frustrated outbursts.

Control and Independence

Your fledgling toddler is beginning to assert her independence, and at this young age, the only way she may be able to do so is to say "no" and throw herself on the floor in a tantrum. While sometimes her mood swings may arise from something out of your control, such as wanting to drink out of a yellow cup when you only have red, other times you may be able to head a tantrum off by offering choices. Asking her whether she'd rather have her cheese on a plate or in a bowl, or whether she'd rather wear the pink or the purple dress, can allow her to have some say over what happens.


Your 18-month old may be cutting molars, which can be painful and can cause irritability, including mood swings and tantrums. Other symptoms include drooling and trouble sleeping or eating. The lack of sleep that teething can cause may contribute to mood swings; you may find that your toddler needs an extra nap during the day if he is up due to teething pain during the night. Ask his pediatrician about the correct dosage of an over-the-counter pain medication, such as acetaminophen or ibuprofen, if he is really uncomfortable. Otherwise, offer cold teething rings and cool drinks to soothe sore gums.

Physical Discomfort

Your toddler may react with mood swings and tantrums when she's feeling uncomfortable. She might be too hot or too cold, tired, hungry or getting sick. Ear infections are common in toddlers, and ear pain can come on suddenly, causing outbursts and irritability. She also may react to the beginning stages of the common cold, which include a scratchy throat and nasal congestion, before you realize that she is getting sick. If you are sure that your toddlers is well-rested, has eaten recently, does not have a diaper rash and is dressed appropriately for the weather, consider calling the pediatrician if she is persistently cranky for no apparent reason.

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