<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-01-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000711665</issuerCik>
        <issuerName>PHOTOMEDEX INC</issuerName>
        <issuerTradingSymbol>PHMD</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001269340</rptOwnerCik>
            <rptOwnerName>MCGRATH DENNIS M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>PHOTOMEDEX, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>147 KEYSTONE DRIVE</rptOwnerStreet2>
            <rptOwnerCity>MONTGOMERYVILLE</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>18936</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

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            <securityTitle>
                <value>PhotoMedex Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2011-01-04</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
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                </transactionShares>
                <transactionPricePerShare>
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                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
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                </transactionAcquiredDisposedCode>
            </transactionAmounts>
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                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
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            </securityTitle>
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            <exerciseDate>
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            <expirationDate>
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                <transactionPricePerShare>
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            <expirationDate>
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        <derivativeTransaction>
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                <transactionPricePerShare>
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            <exerciseDate>
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            <expirationDate>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
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        <derivativeTransaction>
            <securityTitle>
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            <conversionOrExercisePrice>
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            <transactionDate>
                <value>2011-01-04</value>
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            <deemedExecutionDate></deemedExecutionDate>
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                <equitySwapInvolved>1</equitySwapInvolved>
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            <transactionAmounts>
                <transactionShares>
                    <value>1048</value>
                </transactionShares>
                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
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            <exerciseDate>
                <value>2011-01-04</value>
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            <expirationDate>
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                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
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            <exerciseDate>
                <value>2011-01-04</value>
            </exerciseDate>
            <expirationDate>
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            <underlyingSecurity>
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                    <value>PhotoMedex Common Stock</value>
                </underlyingSecurityTitle>
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            </underlyingSecurity>
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    <footnotes>
        <footnote id="F1">Shares issued from the Company's 2005 Equity Compensation Plan, pursuant to a tender offer made under Schedule TO, and amended, whereby the reporting  person exchanged certain options issued under the same Plan.</footnote>
        <footnote id="F2">Reflects the 1-for-6 reverse split on 2/3/2010</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Dennis M. McGrath</signatureName>
        <signatureDate>2011-01-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
